John has two jobs. For daytime work at a jewelry store he is paid $200 per month plus a commission. His monthly commission is normally distributed with a mean of $600 and a standard deviation of $40. At night he works as a waiter, for which his monthly income is normally distributed with a mean of $100 and a standard deviation of $30. John's income levels from from these two sources are independent of each other.
For a given month what is the probability that John's commission from the jewelry store is less than $640?
For a given month what is the probability that John's income as a waiter is between $70 and $160?
Attached Word document gives the probability that John makes money as a waiter or jewelry store worker.