Y and Z walk around a circular track. They start at 5 a.m from the same point in the opposite directions. Y and Z walk at a speed of 3 rounds per hour and 4 rounds per hour respectively. How many times shall they cross each other before 7 a.m
Choose the correct answer:  A) 14  B) 15  C) 16  D) 17  E) 18

Rationale: explanation : relative speed = ( 3 + 4 ) = 9 rounds per hour so , they cross each other 9 times in an hour hence , they cross 18 times before 7 a . m answer : option e
Answer: E