The function y=60/x relates y, the time in hours that it takes Michael to travel to his grandparents’ house, to x, his average speed in miles per hour. What does the number 60 in the function represent? a) the time, in hours, that it takes to get to Michael’s grandparents’ house b) the distance, in miles, that must be traveled to get to Michael’s grandparents’ house c) the fuel, in gallons, that is used to get to Michael’s grandparents’ house d) the rate, in miles per hour, that Michael travels to get to his grandparents’ house