While exercising, a person’s recommended target heart rate is a function of age. The recommended number of beats per minute, y, is given by the function y = f(x) = -0.85x + 187, where x represents a person’s age in years. Determine the number of recommended heart beats per minute for the following ages and explain the results.

(a) 20

(b) 30

(c) 50 

(d) 60

(e) What is the age of a person with a recommended target heart rate of 85?