Webform - Convert field choices in binaries outputs to approve or reject a request

Hey comunnity!
I built a webform to collect answers for 21 questions (single choice: yes or no). If 30% of the questions are incorrect, I should send a reproval e-mail to the user. If not, the user should be approved.
I was thinking to convert the single choices to binaries (0 or 1 depending the question, some are "Yes" for correct answer and others are "No) and at the end, sum up if the result is equal 14 or higher to send the approval. How can I do that? Is it the better approach?

Thank you!