Joseph is a college student at The University of Texas. He made good grades in high school and received a scholarship that pays for his school, housing and books. Joseph does not have a car, but still needs to pay for his own meals. He calculates that he needs to make at least $450 per month. He has a job working at the bookstore and gets paid $15 per hour. What is the minimum number of hours that Joseph must work per week to make $450 per month?
A. 40 hours
B. 7.5 hours
C. 22.5 hours
D. 11 hours