The times for a group of students to complete the physical fitness obstacle course result in a bell-shaped curve. The mean time to finish was 21 minutes with a standard deviation of 4 minutes. Use the Empirical Rules to find:

(a) the percent that took longer than 21 minutes.

(b) the percent that took less than 21 minutes.

(c) the percent that took between 13 and 29 minutes.

(d) What interval of time captured almost all, 99.7%, of the times?