If a certain computer is capable of printing 4700 monthly credit card bills per hour, while a new model is capable of printing at a rate of 6800 per hour, the old model will take approximately how much longer than the new model to print 10000 bills? Select:
A) 19 mins	B) 29 mins	C) 39 mins	D) 38 mins	E) 37 mins

Rationale: old model ' s 1 hr work = 4700 new model ' s 1 hr work = 6800 old model ' time taken to print 10000 cards for 1 hr - - 4700 cards x - - 10000 x = 10000 / 4700 = 100 / 47 new model ' time taken to print 10000 cards for 1 hr - - 6800 cards y - - 10000 y = 10000 / 6800 = 100 / 68 x = 10000 / 4700 = 100 / 47 = 2 6 / 47 hr difference is 100 / 47 - 100 / 68 = 6800 - 4700 / ( 47 * 68 ) 2100 / 3196 = 0.66 hrs = > 39 minutes old model ll take 39 minutes longer to print 10000 cards than new model ans : 39 mins answer : c
Answer: C