(Solved): There are four boxes, each containing five coats: a red coat, a blue coat, a green coat, a yellow c ...
There are four boxes, each containing five coats: a red coat, a blue coat, a green coat, a yellow coat and an orange coat. Four people take a box each, and the four people independently pick a coat at random from their box and put it on. What is the probability that at least two people are wearing a coat of the same colour?