For the equation 4(2x-3)-(mx+5)=5x+b to be an identity, which of the following must be true about the constants m and b? Show your work

(1) m = 3 and b = -7
(2) m = 8 and b = 17
(3) m = -3 and b = -15
(4) m = 3 and b = 17