Customer Service Stars = Numbers Variable?

I'm doing a customer service scenario. Based on their response to questions, they earn or lose stars. The goal being to finish the scenario with a 5 star rating. 

I was thinking I would set up a number variable. But I'm not sure.

Example: if choose A (right answer) they get another star. If choose B (okay answer, but not best practice) stars stay the same. If choose C (Wrong answer) they lose a star. Then go to next question and amount of stars carry over and they get opportunity to add more stars. Repeat.

The number variable would help keep track of the stars they earn, I think?

Am I on the right track, or is there a better way to set this up.

Thanks!