Interger, goal and nonlinear programming models

A cleaning crew currently spends 6 hours per house cleaning 8 houses everyday, for a profit of $15 per hour. The crew now wants to offer its services to other houses, as well as small professional offices. The crew believes it will take 7 hours to clean the office of a lawyer and that the profit for doing so will be $19 per hour. It will take 10 hours to clean a doctor's office and that the profit for doing so will be $25 per hour. The crew can make 120 hours of labor available per day and does not want to cancel any of its existing house contracts. What is the best mix of homes and offices to clean per day to maximize profit? Remember that your solution must be in whole numbers.

Please explain solution and show in excel and Solver.