Sum from dropdown selection

Good evening all, 

I'm sorry if this has already been answered!

I have a spreadsheet with multiple options in a drop down list for multiple cells.

I need to be able to generate a sum from three specific drop down selections for each of the three results to go into their own separate cell. I was wondering if anyone knows the formula for this?

Just to confuse things, there are also several drop down selections that will be the same sum category. However that part is not essential as I can do that sum individually. 

I do hope you can help!