\begin{aligned} & \text { [Combinations and Permutations]} \\ & {[\text { Rule of Product }]}\end{aligned}

Nina has 7 different chocolate candies, and Kolya has 9 different caramels. In how many ways can they exchange five candies with each other?
See the solution to problem 30690.

## Answer

$C_{7}^{5} C_{9}^{5}=C_{7}^{2} C_{9}^{4}=2646$ ways.

## Problem