Which system models the height of the tennis ball and the height of the dog's mouth over time? h = 4.5t + 18 and h = -16t2 + 1.5t + 21 h = 18t + 4.5 and h =-16t2 + 21t + 1.5 h = -16t2 + 4.5t + 18 and h = -16t2 + 1.5t + 14 h = -16t2 + 18t + 4.5 and h = -16t2 + 21t + 1.5