The field mouse population in Example 1 satisfies the differential equation dp/dt=0.5p−450

The field mouse population in Example 1 satisfies the differential equation dp/dt=0.5p−450.
a) Find the time at which the population becomes extinct if p(0)=850.
b) Find the time of extinction if p(0)=p0, where 0<p0<900.
c) Find the initial population p0 if the population is to become extinct in 1 year.