The quadratic x2−8x+15 can be written as (x+m)(x+n) where m and n are integers. Which of the following correctly describes the signs of m and n?
(a) One of m or n is positive and the other is negative
(b) Both m and n are negative
(c) Both m and n are positive
(d) m and n are not integers (the quadratic is not factorable over integers)