5a. How many ways can you select a committee of size 4 from a group of 10 people if 2 of the people refuse to serve together? b. How many ways can you select a committee of size 4 from a group of 10 people if 2 of the people will only serve if they are together? 6. Fifty Martians are together. What's the probability at least 2 of them share the same birthday? .