$$Totalcars=16$$

where

$$mimivans=6,sedans=7andhatchbacks=3$$

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

$${}^{16}{C}_3=\frac{16\times 15\times 14}{3\times 2\times 1}=8\times 5\times 14$$

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

$$6\times 7\times 3$$

$$\therefore Probability=\frac{6\times 7\times 3}{8\times 5\times 14}=\frac{9}{40}$$

So choice J is correct.