1. If d/dx(f(x)) = g(x) and if h(x) = x^2, then d/dx(f(h(x)) = ?

A) g(x^2)

B) 2xg(x)

C) g'(x)

D) 2xg(x^2)

E) x^2g(x^2)

I got A,

d/dx(f(h(x))

= g(h(x))

= g(x^2)

Not 100% sure it that's right so I'd like to get someone to check it please.

2.

In the figure, AB is a 40 ft ladder with end A against a vertical wall and end B on level ground. If the ladder is sliding down the wall, what is the distance BC at the instant when B is moving along the ground 3/4 as fast as A is moving down the wall?

I derived pythagoreans theorem to get

2x(dx/dt) + 2y (dy/dt) = 0

The problem is I don't have values for either x or y and I'm not sure how to get them.