If 5/w + 5/x = 5/y and wx = y, then the average (arithmetic mean) of w and x is  Choose the correct choice from the following.
A) 1 / 2	B) 1	C) 2	D) 4	E) 8

Rationale: "given : 5 / w + 5 / x = 5 / ywx = y find : ( w + x ) / 2 = ? 5 ( 1 / w + 1 / x ) = 5 ( 1 / y ) - divide both sides by 5 ( 1 / w + 1 / x ) = 1 / y ( x + w ) / wx = 1 / wx - sub ' d in y = wx x + w - 1 = 0 x + w = 1 therefore ( w + x ) / 2 = 1 / 2 ans : a"
Answer: A