1. How many primes p have the property that p+10 and p+20 are also primes?

2. A 5 digit number M2M2M (where M is a digit from 0 to 9) is divisible by the two digit number MM. Find M.

3. Find the remainder of 10! upon division by 99. You may use the fact that (p-1)!/p has a remainder of p-1 for all primes p.