If (mx + 7) (5x + n) = px^2+15x+14, what is m (n+p) ?

A) - 10

B) - 520

C) 480

D) 2

E) 520

(mx + 7) (5x + n) = 5mx^2 + mnx + 35x + 7n

= 5mx^2 + (35 + mn) x + 7n

= px^2 + 15x + 14

7n = 14

n = 2

35+mn = 15

35 + m (2) = 15

35 + 2m = 15

2m = 15-35

2m = - 20

m = - 10

p = 5m

= 5 (-10)

=-50

m (n + p) = - 10 (2 - 50)

= 480

The answer you are looking for is C