George wants to sell toy rockets at the state fair. He can purchase these rockets at $0.50 each and can return all unsold rockets for a refund. He will be required to rent a booth from which he can sell the rockets at a flat rate of $200, payable in advance. The rockets will be sold at $0.90 each. a. How many rockets must be sold to break even? b. How many rockets must be sold to make a profit of $1,000 for the week?