Definition: You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
Input: Question: A man rows his boat 78 km downstream and 56 km upstream, taking 4 hours each time. Find the speed of the stream?

 Option A: 6

 Option B: 5

 Option C: 7

 Option D: 8

 Option E: 3

Option E