Question 1131697
The exponential probability distribution can be written as:
P(x) = k*exp(-kx), where k is a constant
The mean of this distribution is given by 1/k
Since the taxi arrivals are independent random events, the fact that you have
already been waiting an hour has no bearing on what happens in the next 9
minutes.
To determine P(60 <= x <= 69), we need to integrate P(x) from 60 to 69, 
with k = 1/26.23 = 0.03812
The indefinite integral is -exp(-kx)
Thus P(60 <= x <= 69) = -(exp(-0.03812*69) - exp(-0.03812*60)) = 0.02949