If a certain computer is capable of printing 4900 monthly credit card bills per hour, while a new model is capable of printing at a rate of 6600 per hour, the old model will take approximately how much longer than the new model to print 10000 bills?
Choose the correct answer.
A) 31 B) 76 C) 88 D) 26 E) 81

Rationale: "explanation : old model is capable of printing at a rate of 4900 per hour new model is capable of printing at a rate of 6600 per hour old model time taken to print 10000 cards = 10000 / 4900 = 100 / 49 new model time taken to print 10000 cards = 10000 / 6600 = 100 / 66 old model – new model : 100 / 49 - 100 / 66 = 1700 / ( 49 × 66 ) = 850 / ( 49 × 33 ) = 0.525 hrs = > 31 mins therefore , the old model will take approximately 31 mins longer than the new model to print 10000 bills answer : a"
Answer: A