Creating an Invoice with If, Then, Else

[Purple22724798rs1d]

Total newb to javascript, so pardon my ignorance, but your help would be so much appreciated.

I want to create an invoice with Fields A, B, and C.

What I want C to do:
If A*B is >1 and <50, then C = 50

If A is blank or =0, then C is blank.

Also, would I put the script in the Custom calculation script or Custom Validation Script or elsewhere?
Thank you.

[Nesa Nurani]

What happen if result is not between 1 and 50?

Use script as custom calculation script of field C:

var a = Number(this.getField("A").value);
var b = Number(this.getField("B").value);
var x = a*b;
if(x>1 && x<50)
event.value = 50;
else if(a == "")
event.value = "";

[Purple22724798rs1d]

Thank you so much for your answer. I will give it a try when I have more time later today.

If the result is >50, then the result is A*B.

So what I'm wanting to do is apply a minium fee if the total does not meet a specific amount. 

[Purple22724798rs1d]

Sorry, to clarify, if A*B is >50, then display the actual result of A*B.