Sum If Question - Example Attached

Attached a sheet for example

The user will select a company from the drop down list in Sheet Input Assessment

Goal
In Impact Assessment Sheet, Cell B13 will look up company defined in B5 from Consolidated data. The output will align to the descriptions in cell b11 and a 13. This will repeat for Company 1 -4. The sum will be divded by the number of companies. If 3 is selected and one is blank then divide by three.

For example
Company 1 Company 2

Cell B13 would first look up Company1 from the consolidated sheet and the output would be 1.
Cell B13 would look up Company2 from the consolidated sheet and the output would be 0.

Since only 2/4 is selected the number would be averaged by 2.