The perimeter of an equilateral triangle is 60. If one of the sides of the equilateral triangle is the side of an isosceles triangle of perimeter 50, then how long is the base of isosceles triangle?  Choose the correct choice from the following.
A) 5	B) 10	C) 15	D) 20	E) 25

Rationale: "the base of the isosceles triangle is 50 - 20 - 20 = 10 units the answer is b ."
Answer: B