Calling an F# Function from C#

I've looked at other instructions and still have no idea how to do this. I have two projects (Calculator in C# and Logic in F#). I added a reference to Logic in Calculator, as well as a reference to FSharp.Core

However when I add the line

float result = Logic.start(formula);

In my C# project, I get an error saying:

"The name Logic does not exist in the current context."

There is a module Logic in the logic project, so it should show up right? What am I still missing?

EDIT: Here's the function definition...

let start formula =
core (List.ofSeq formula) [] []