Logical test function problem

I need to figure out how to get the proper entry into a cell based on two other cells. Specifically:

Cell Q4 needs to display text letter X, text letter E, or blank. 0 (zero) is acceptable since they are suppressed.

If DP4 is X then Q4 needs to be X.
If DP4 is blank and DS4 is X then Q4 needs to be E.
If both DP4 and DS4 are blank then Q4 needs to be blank or zero.
If both DP4 and DS4 are X then Q4 needs to be X.

I'm lost in how to accomplish this.

Thanks for any help!
Tom

You do not need to account for your fourth condition, because there is no scenario where condition 1 is false and 4 is true or visa versa.

=if(exact(dp4,"X"),"X",if(and(isblank(dp4),exact(ds4,"X")),"E",""))

=if(exact(dp4,"X"),"X",if(and(isblank(dp4),exact(d s4,"X")),"E",""))

Notice the space in the formula in the middle of ds4. It didn't work at first but when I removed the space it works fine!

Thank you so much!

Tom