There are 28 stations between Ernakulam and Chennai. How many second class tickets have to be printed, so that a passenger can travel from one station to any other station?  Choose the correct choice from the following: A) 800 B) 820 C) 850 D) 870 E) 900

Rationale: "the total number of stations = 30 from 30 stations we have to choose any two stations and the direction of travel ( ernakulam to chennai is different from chennai to ernakulam ) in 30 p 2 ways . 30 p 2 = 30 * 29 = 870 answer : d"
Answer: D