Let a and b be positive integers. The sum of the coefficients of the polynomial
$$P ( x ) = ( x + a ) \cdot ( x + b )$$
is 15. What is the sum $a + b$?
A) 10
B) 9
C) 8
D) 7
E) 6
Let a and b be positive integers. The sum of the coefficients of the polynomial

$$P ( x ) = ( x + a ) \cdot ( x + b )$$

is 15. What is the sum $a + b$?

A) 10\\
B) 9\\
C) 8\\
D) 7\\
E) 6