Problem Solving (PS) | If 50 apprentices can finish a job in 4 hours and 30 skilled workers

I got B. This would be a classic problem where I'd make a silly mistake, but it appears I might have avoided that.

If 50 apprentices can finish a job in 4 hours and 30 skilled workers can finish the same job in 9/2 hours, how much of the job should be completed by 10 apprentices and 15 skilled workers in 1 hour?

I knew I needed to find the individual rates of one worker per hour. If it takes a 50 workers 4 hours, that collectively means it takes the apprentices 200 total hours to compete the
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