$$ Total\ cars=16 $$

where

$$ mimivans=6,\ sedans=7\ and\ hatchbacks=3 $$

Thalia will rent 3 cars chosen randomly. So the number of combinations of selected cars is

$$ ^{16}C_3=\frac{16\times15\times14}{3\times2\times1}=8\times5\times14 $$

The number of combinations of renting 1 of each of the 3 types of cars is

$$ 6\times7\times3 $$

$$ \therefore Probability=\frac{6\times7\times3}{8\times5\times14}=\frac{9}{40} $$

So choice J is correct.