Nested If Funtion Question.

Hey, I am trying to replicate this chart here (see the image), I am given ABCD, and I need to create formulas for EFG. I am a total "nub" when it comes down to Exel so please don't judge. If you can help, thank you kindly, if you can't sorry for wasting electricity.
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E2 and down: =SUM(C$2:C2) & "-" & SUM(D$2:D2)

F2 and across and down: =IF(C2, SUM(F1,C2), "")

I tried to use those formulae but they don't work. Here is what i got:
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okay, thnx Mod i figured it out. Awesome help.