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