Adding on call hours for different days

I am trying to calculate on call hours. The problem is that from Sunday to Wednesday it is 5 hours and from Thur to Sat it i s 4 hours. I got it to add regular on call at 4 hours but can't seem to make it add in the 5 hour diff. I have so far this formula...
=COUNTIF(B4:Q4,"D-C")*4+COUNTIF(B1:Q4,"E-C")*4
The D-C is day on call and the E-C eve on call value.

Can anyone figure out a way to make it check to see if it's Sun to Wed and make it add 5 instead of four?

Thanks