Dylan uses the expressions $\left(x^2-2 x+8\right)$ and $\left(2 x^2+5 x-7\right)$ to represent the length and width of his bedroom. Which expression represents the area ($lw$) of Dylan's room?

A$2 x^4-10 x^2-56$

B$2 x^4+10 x^2+56$

C$2 x^4+x^3-x^2+54 x-56$

D$2 x^4+9 x^3+33 x^2+54 x+56$