Atoy ball in the shape of a sphere expands and contracts. when it is completely closed, it has a diameter of 19.5 inches. find the volume of the sphere when it is completely closed

Ian is in training for a national hot dog eating contest on the 4th of july. on his first day of training, he eats 4 hot dogs. each day, he plans to eat 110% of the number of hot dogs he ate the previous day. write an explicit formula that could be used to find the number of hot dogs ian will eat on any particular day.