This sounds simple but is proving tricky

I have row of booleans a1:l1 and want to sum rows below that

a3:l7

according to the booleans value, but how could this be done in 1 cell

sumif wont work because the ranges are different shapes so it only does row 3.

I think the problem is row/column ambiguity

of course you could sub total rows or columns or do multiple sumifs in one
cell, but is there a better way?

Cheers