This is a very good example of why you don't want to waste time actually solving for a value in a data sufficiency question.

Statement 1: This is essentially saying that P is the 100th prime number. Because the distribution of primes doesn't follow any predictable pattern, there is no formula to find the nth prime number. However, if we had all day, we could certainly start listing prime numbers until we got to the 100th one, and that would be the value of P. SUFFICIENT

Statement 2: Same idea. If you count up how many of the numbers between 1 and 3912 are prime, this value would be equal to P. It would take forever, but we could do it. Of course the important thing is that it would be a definite, unique value. We don't actually care what that value is. SUFFICIENT.

So the answer is D