The area of a circle is added to its diameter, and the circumference is then subtracted from this total, the result is 10. What is the radius of the circle?	Pick
A) 2 * pi B) pi C) 2 D) 4 * pi E) 4

Rationale: the equation is ; diameter + area - circumference = d + a - c = d + pi * r ^ 2 - 2 * pi * r = 2 r + pi * r ( r - 2 ) . by plugging in the answers we can test the answers quickly ; then , 4 is the only possible answer . answer : e
Answer: E