David ran the 50 yard dash in 7.2 seconds and won the event. justin came in the second with a time of 8.1 seconds. how much better was david's time than justin's?

Ben frank is an electrician who installs lighting fixtures. he charges (in dollars) his clients 15h+40f15h+40f where hh is the number of hours worked and ff is the number of fixtures installed. how much does ben frank charge when he works 77 hours and installs 99 fixtures?