79. Tara's heart rate during a workout is modeled by the differentiable function h, where h(t) is measured in beats per minute and t is measured in minutes from the start of the workout. Which of the following expressions gives Tara's average heart rate from t = 30 tot = 60 ? (A) (B) (D) h(t) dt 30 1 60 30 30 h(t) dt 1 60 300 h (1) dr h' (30) +h' (60) 2