On average, it takes 15 minutes for Humphrey to walk to school, and the distribution is normal with a standard deviation of 3 minutes. On the other hand, it takes 12 minutes for Rebecca to walk to school on average. The distribution is also normal, with a standard deviation of 5 minutes. Suppose that the time it takes for Humphrey and Rebecca to arrive school is independent of each other.

1. What is the probability that Humphrey will attive earlier than Rebecca?

2. In order to arrive first with 95% probability, how many minutes earlier does Humphrey need to begin walking?