Cvp analysis study text section a practice

Good afternoon,

I have been trying to solve the section a questions on the study text but I seem to consistently fail on the weighted average…
Example in question 28 section A shouldn’t we do contribution of single product multiplied by (single product unit/total units) like this:
7*(2/12)?

I was under the impression that we don’t just multiply it by the number of units otherwise is not a weighted average…

Am I thinking wrong?

Thank you

Regards,

Cristina