Match each function definition of the binary operator + function to its correct description. Assume that functions defined outside of the class are appropriately prototyped in the class.

1) foo foo::operator+(foo f) { . . . . }

2) foo operator+(foo f1, foo f2) { . . . . }

3) friend foo operator+(foo f1, foo f2) { . . . . }

4) foo operator+(foo f) { . . . . }

a) member defined in the class

b) member defined out of the class

c) non-member defined in the class

d) non-member defined out of the class