For the Pair of Functions, Find the Product $(f g)(x)$
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Multiple Choice

For the pair of functions, find the product $(f g) (x)$ .
- $f(x) =5 x+3, g(x) =-4 x-7$

A) $-21 x^{2}-49 x-23$
B) $-18 x^{2}+47 x-21$
C) $-20 x^{2}-47 x-21$
D) $20 x^{2}+47 x-21$