I need some help with a formula. Here's my data:

Field F7 could be 50 or 60 (value)
Field F8 could be either Y or N (meaning yes or no)

If F7=50 and F8=y, then I need it to read "NA" for not applicable
If F7=50 and F8=n, then I need it to read " " blank
If F7=60 and F8=Y, then I need it to perform calculation of F5*F4
If F7=60 and F8=n, then I need it to read " " blank

So, only when F7 is 60 and F8 is Y do I want the formula to calculate. How
do I do this? I've tried =ifand statements and =ifor statements, but they
all keep coming up "false". Please help!