Question 65
Julia is learning how to write the letter $C$. She has $6$ differently-colored crayons, and wants to write $Cc\ Cc\ Cc\ Cc\ Cc$. In how many ways can she write the ten $C$s, in such a way that each upper case $C$ is a different color, each lower case $C$ is a different color, and in each pair the upper case $C$ and lower case $C$ are different colors?