The shelf life (in hours) of a certain perishable packaged food is a random variable whose probability density function is given by
f(x)=20,000/((x+100)^3) for x>0 and =0 elsewhere
Find the probabilities that one of these packages will have a shelf lift of
(a) at least 200 hours
(b) at most 100 hours
(c) anywhere from 80 to120 hours