During the summer, kurt works on his uncle's goat farm. one of kurt's many chores is to milk the goats. the proportional relationship between the number of hours milking, x, and the number of goats milked by kurt, y, can be modeled by the equation y = 6x. if kurt milked 21 goats, how many hours did it take? a) 3 b) 3.5 c) 4 d) 4.5