Simplify:

(−7a−4b7)(3a2b−4)
(1 point)
Responses

−21b3a2
the fraction with numerator negative 21 b cubed and denominator A squared

−21a6b3
the fraction with numerator negative 21 and denominator A to the 6th power b cubed

−21a8b28
the fraction with numerator negative 21 and denominator A to the 8th power b to the 28th power

−21a2b3