If function troubles

"If" is to short to search the forums for and I am horrible at finding things. So I'm sorry if this has been discussed before. (Which I'm sure it has)
Here's what I need:
IF C4 says "MF" use this formula =(D4-E4)*0.75
but IF C4 says "SU" use this formula =(D4-E4)*1.25

What if it contain neither?

=(D4-E4) * IF(C4="MF",0.75,IF(C4="SU",1.25,1))

Ok I see how it works now! Thank you so much

If if contains neither then there is no need for the formula at all.

If you want no result if neither match is made then the final 1 in the formula just needs to be replaced with "" (an empty string).

Anyway, glad to have helped - if this one's done then please remember to edit your original post to mark this thread as solved. Thanks.