Miguel Indurain, a five-time winner of the Tour de France, has the lowest recorded resting heart rate, 28 beats per minute (bpm). This is less than half the normal rate, which is about 66 bpm. Which of the following equations, where t represents time in minutes and bb the number of beats, represents a heart rate greater than Indurain's?
a. b=15t)
b. b=25t
c. b=30t
d. b=40t