So,
This is independent probability.
First, we have the two people.
[tex] \frac{1}{2} [/tex]
Then, we have 3 different toppings.
[tex] \frac{1}{2}* \frac{1}{3} = \frac{1}{6} [/tex]
Next, we have 4 possible types of crusts.
[tex] \frac{1}{6} * \frac{1}{4} = \frac{1}{24} [/tex]
Finally, we have the 8 possible toppings.
[tex] \frac{1}{24} * \frac{1}{8} = \frac{1}{192} [/tex]