A train travels at a speed of 40 kmph through urban areas, 50 kmph in suburban areas and 75 kmph in rural areas. If the trip of train has half-an-hourtravel in urbanareas, $$3\frac{1}{2}$$ hours through suburbanareas and 3 hours in rural areas then the average speed (in kmph)of the train during the entire trip is

A

52

B

55

C

60

D

62