In one hour, a boat goes 11km along the stream and 5 km against it. Find the speed of the boat in still water	Choose the correct choice from the following answers:
A) 6 B) 7 C) 8 D) 9 E) 10

Rationale: "explanation : we know we can calculate it by 1 / 2 ( a + b ) = > 1 / 2 ( 11 + 5 ) = 1 / 2 ( 16 ) = 8 km / hr answer is c"
Answer: C