Calculate Weighted Average for specific attributes

Hi, 

I am having difficulty in trying to calculate the weighted average from the dataset I have. 

I have unpivoted the data in query editor due to the nature of the data in the source. 

I want to work out the total weighted average per column e.g total weighted average for sp £/t, cos £/t and margin £/t. The Total row should show the weighted average

Expected: 

To calculate this for e.g sp £/t, i need to multiply tonnes by the sp £/t value so - ((50 * 2000) + (0*0) + (20*4000))/70

Below is the source table - 

Any help is appreciated! 

Thanks