Muscle Street Gym charges an initial fee of $99 and $15 per month. Which of the following functions model the total cost of being a member at Muscle Street Gym?

Gravel is being dumped from a conveyor belt at a rate of 25 ft3/min, and its coarseness is such that it forms a pile in the shape of a cone whose base diameter and height are always equal. how fast is the height of the pile increasing when the pile is 14 ft high? (round your answer to two decimal places.) ft/min