(Please help my test is timed.) The amount of time, t, Tom needed to mow the grass in his neighborhood is directly proportional to the amount of lawns, I, (all the same size) and inversely as the number of friends, f , who helped Tom. If it takes Tom and one friend 5 hours to mow 10 lawns, how long will it take Tom and 3 friends to mow 24 lawns?