Consider T as total time taken to record 420 page book. Average time 90 secs = 1.5 mins.

So question asks is total time T < 420*1.5 i.e.

T<630?1) Each tape was at most 40 minutes

INSUFFICIENT: We dont know how many tapes were recorded

2) The book was recorded on 15 tapes

INSUFFICIENT: We dont know how long each of those 15 takes took for recording

Combining (1) and (2) --We need to prove

T<630?

SUFFICIENT: Tape (out of 15 tapes) spent

at the most 40 mins (i.e.

less than or equal to 40)

Maximum time that could have spent on recording = 15 * 40 = 600 (which is still less than 630)

Hence choice(C) is the answer. _________________

Thanks,

PraPon

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