Large people arrive at your doorstep according to a Poisson process with rate b; and small people arrive at your doorstep according to an independent Poisson process with rate c. Assume both processes have been going on forever. Fix a time t to be 1 o'clock. What is the expected length of the interval that t belongs to? That is, find the expected length of the interval from the last event before t until the first event after t. Here, an event refers to the arrival of either kind of people