IF with Multiple Conditions

Using the following formula.

IF(E47="1",B49-0.75,IF(E47="2",B49-0.5,IF(E47="3",B49-0.25,IF(E47="4",B49,""))))

Cell B49 is a SUM Formula - SUM(B5:B15,B19:B23,B28:B38,B43:B44)/5

Cell E47 contains an IF formula as well - IF(E8="Y",D44,IF(E8="N",0,""))

What I would like my original IF forumula to do is look at cell E47 and if there is a "1" take cell B49 and subtract 0.75, if 2, subtract 0.50, if 3, subtract 0.25. If 0 subtract nothing.

Am I on the right track with this?

Or should I look at combining the first IF and SUM forumulas into one?

Thanks,

JT