We can rephrase the question here and another way to think about the question is the total number of second less than 37,800 (90 *420)?
With statement 1, we have no idea how many tapes there are so we can't calculate the total time. So statement 1 is not sufficient. Eliminate A and D.
With statement 2, we have no idea how long the tapes are. So again we can't calculate the total time. So statement 2 is not sufficient. Eliminate B.
With both statements we can calculate the total time is no more than 36,000 seconds (40 *60*15). So then we know the total time is less than 37,800. So the answer is C.
Take care,
Sionainn
BA - Stanford University, MPP - Harvard University
Instructor, tutor for Princeton Review and Airbnb host
In other words a blend of Jamie Escalante from Stand and Deliver, Julie from The Love Boat, and Schneider the Super from One Day at a Time.

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