Assessment Help - Scoring for Speed and Accuracy

I'm looking for some recommendations on scoring a measure. I am working on providing scoring recommendations for an employee selection test my company built. One of our measures is intended to measure time sharing/multitasking. Respondents answer 15 "distractor" questions (simple addition and subtraction) while listening to an audio clip which provides information that they are then tested on (5 questions). The 5 substantive questions are most important, but we also want an applicants' total score on the measure to account for the number of distractor questions that they complete and the number of distractor questions that they get right. An added challenge is that we have to apply weights to items in our internal applicant tracking system, which limits the types of analyses I can use. Anyone have experience with a similar test? Any recommendations would be much appreciated!

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