calculate weighted average while ignoring null values (without using sumproduct)

I need a formula that can be used calculate a weighted average without using SUMPRODUCT (it . I've been banging my head all night, and feel that there's undoubtedly a way to utilize the ratio between the weights to calculate these values - but I am stuck.

Any help would be appreciated, and I've attached a sample.

Here's an image for those that don't want to download the image. TXgFBLR.png