It's 6:00 P.M., and Amy has to stay in the office until her sister Isabel calls her. After each full hour that Amy is in the office, there is a 70% chance Isabel will call her. What is the probability that Isabel calls her at 9:00 P.M., and no sooner?
a)0.027
b)0.063
c)0.09
d)0.147
e)0.343
a)0.027
b)0.063
c)0.09
d)0.147
e)0.343
