#### Answer

a) 69.6 $\frac{heartbeats}{minute}$
b) 71.75 $\frac{heartbeats}{minute}$
c) 71 $\frac{heartbeats}{minute}$
d) 66 $\frac{heartbeats}{minute}$
Conclusion: We can find the slope at t = 42 by the average of the closest slopes which are t = 40 and t = 44, so m = $\frac{71+66}{2}$ = 68.5 $\frac{heartbeats}{minute}$

#### Work Step by Step

To find the slopes calculate by:
m = $\frac{\frac{heartbeats}{minute}_{tf} -\frac{heartbeats}{minute}_{ti} }{tf-ti}$
a) m = $\frac{2948-2530}{42-36}$
b) m = $\frac{2948-2661}{42-38}$
c) m = $\frac{2948-2806}{42-40}$
d) m = $\frac{3080 - 2948}{44 - 42}$