3.21: 5-digit numbers and red/brown hair arrangements

Five of the digits 1, 2, 3, 4, 5, 6, 7, 8, 9 are used to make a 5-digit number. Find how many ways this can be done when the 5-digit number is greater than 50 000.

In a group of 13 people, 7 have red hair and 6 have brown hair. The 13 people stand in line for a photograph. No person with red hair is standing next to another person with red hair. Find the number of different ways this can be done.

Chris chooses 5 people from this group. Find the number of ways Chris can do this if at least 1 person chosen has brown hair.