Having trouble detecting my mistake in my coding

I am still new to C programming and I am having a bit of a problem in my coding. I am aware that I can't just ask for help without trying to fix it by myself first, so I tried fixing it and is still having the same problem.

My problem is, my coding displayed an incorrect calculation like below.

            ORDER PRICE SUMMARY
===========================================
 Customer No.      Total Order Price(RM)
===========================================
      1                  RM 40.00
      2                  RM 40.00
      3                  RM 478664371470163710000000000000000.00
===========================================
 Grand Total             RM 478664371470163710000000000000000.00
===========================================

Customer 1 and 2 showed the correct price but it just got messed up for Customer 3, which affects the grand total.

My coding is below, and it is obvious that I am using the simplest way of writing my code since my goal is to just answer a coding question.

#include <stdio.h>

float calculatePrice(char);
void main()
{
  char comboType, addon;
  int comboQty, addonQty,i=1,j=1;
  float orderPrice = 0.00, comboPrice, addonPrice, grandPrice=0.00; // new float
  float customerPayment[3], allPrice[3]; // declare array



  printf ("--------------------------------------------------------------\n");
  printf ("                     ~ SATAY RESTAURANT ~                     \n");
  printf ("--------------------------------------------------------------\n");
  printf (" Combo Type                  Item                  Price (RM) \n");
  printf ("--------------------------------------------------------------\n");
  printf ("     A        25 Chicken Stay + 25 Beef Satay        40.00\n");
  printf ("     B        30 Chicken Stay + 20 Mutton Satay      52.00\n");
  printf ("     C        10 Mutton Stay  + 40 Beef Satay        46.00\n");
  printf ("   Add-On      1 Ketupat                              0.60\n");
  printf ("--------------------------------------------------------------\n");

  for (j=0;j<3;j++)
  {
      printf("\n Customer %d\n",j+1);
      printf("-------------");
      printf("\n Enter Combo Type (A/B/C or X to end)  : ");
      scanf(" %c", &comboType);

      while (comboType != 'X' && comboType != 'x') // start while loop
      {
          comboPrice =  calculatePrice (comboType);
          printf(" Order Price for Combo %c               : RM%.2f \n ", comboType, comboPrice);
          printf("\n Enter Combo Type (A/B/C or X to end)  : ");
          scanf(" %c", &comboType);
          allPrice[j] += comboPrice;
      }

      printf("\n Add-On Ketupat (Y/N)                  : "); // if X, ask for add-on
      scanf(" %c", &addon);

      if (addon != 'N' && addon != 'n')
      {
         printf(" Enter Ketupat Quantity                : ");
         scanf("%d", &addonQty);
         addonPrice = 0.60 * addonQty;
         allPrice[j] += addonPrice;
         printf(" Order price for Ketupat               : RM%.2f\n",addonPrice);
      }

      printf("\n Total Order Price for Customer %d      : RM%.2f\n\n",j+1, allPrice[j]);
      customerPayment[j] = allPrice[j];
  }

  printf("\n\n\n\t    ORDER PRICE SUMMARY ");
  printf("\n===========================================");
  printf("\n Customer No.      Total Order Price(RM)");
  printf("\n===========================================");

  for (i = 0; i<3; i++)
  {
      printf("\n      %d                  RM %.2f",i+1,customerPayment[i]);
      grandPrice += customerPayment[i];
  }

  printf("\n===========================================");
  printf("\n Grand Total             RM %.2f",grandPrice);
  printf("\n===========================================");

  getch ();
}

float calculatePrice (char comboType)
{
  float comboPrice, allPrice = 0.00;
  int comboQty;

     printf(" Enter Quantity                        : ");
     scanf("%d", &comboQty);

       if (comboType == 'A' || comboType == 'a')
        {
         comboPrice = 40.00 * comboQty;
        }

       if (comboType == 'B' || comboType == 'b')
        {
         comboPrice = 52.00 * comboQty;
        }

       if (comboType == 'C' || comboType == 'c')
        {
         comboPrice = 46.00 * comboQty;
        }

        return comboPrice;
}

It would be greatly appreciated if someone could help detecting my mistake.