A person walking at 10 Kmph reaches his office 10 minutes late. If he walks at 15 Kmph, he reaches there 10 minutes earlier. How far is the office from his house?	Choose the correct choice from the following answers:
A) 5 km	B) 15 km	C) 8 km	D) 10 km	E) 20 km

Rationale: formula = s 1 * s 2 / s 2 - s 1 * t 1 + t 2 / 60 = 10 * 15 / 5 * 20 / 60 = 30 * 20 / 60 = 10 km answer is d
Answer: D