Python create a new column with if condition

I tried to create a new column for my dataset with conditions, however, my jupyter shows the erroe:ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Here is my target:

Create a new column called ‘ind_comp’ that displays either 'Above' or 'Below'. Companies with 'pbk' equal to or higher than 'ind_pbk' should have a value‘Above’. The remainder should be ‘Below’.

And my Codes:

def cat(col1,col2):
    if col1-col2>=0:
        result="Above"
    else:
        result= "Below"
    return result

rsh_df['ind_comp']=cat(rsh_df['pbk'],rsh_df['ind_pbk'])

How can I fix this? Thanks