sumproduct formula for horizontal data

Hi,

I have data arranged horizontally, like this

Column A / B / C / D
Row 1 Channel1
Row2 Sales / Supplier Price / Return % / Margin %
Row3 values
And then the same columns repeat for channel 2

I want to calculate a weighted average for all channels for the return %. I would need a formula multiplying the sales columns with the return% columns, summing up the values and dividing by the sum of the sales. I tried sumproduct but I don't get the correct result. Any ideas how to make it work?

Thanks!