1. Set S consists of the integers from -1 to 5, inclusive. If N is the product of three distinct members of Set S, how many unique values of N are there?
2. A combination lock has three dials, each consisting of a single digit, 0-9. The lock can be opened only if each dial is in the correct position. If the code for the lock consists of three prime numbers, what is the probability that 252 is the code? (Provide answer in fraction form).
3. Twelve doctors are to be selected by hospital staff to sit on a six-person committee. Within that committee, an additional subcommittee of three doctors will be formed. How many unique sub-committees are possible?