Answer
$22$, or (G)
Work Step by Step
We are looking for the x at which $C(x) = 120$.
$C(x) = 200e^{-0.02295x} = 120$
Isolate the exponential, and divide both sides by 200:
$e^{-0.02295x} = 0.6$
Take the ln of both sides, $-0.02295x = \ln(0.6) = -0.51$
Solve for $x$ by dividing by $-0.02295$: $x = 22.26$
