The carousel at an amusement park has 20 horses spaced evenly around its circumference. The horses are numbered consecutively from 1 to 20. The carousel completes one rotation about its axis every 40 seconds.

a. What is the central angle, in degrees, formed by horse #1 and horse #8?

b. What is the speed of the carousel in rotations per minute?

c. What is the speed of the carousel in radians per minute?

d. A child rides the carousel for 6 minutes. Through how many radians will the child pass in the course of the carousel ride?