4. Drew is going to try out for the basketball team, so he decides to shoot free throws every day at the park. On the first day, he shoots 15 free throws. On the second day, he shoots 25 free throws. On the third day, he shoots 35 free throws, Drew continues to increase the number of free throws he shoots each day by the same amount. a) If Drew continues to follow this pattern, how many free throws will Drew shoot on the 20th day? b) What is the total number of free throws Drew shot during those 20 days?