A molecule leaves a cell at rate = 0.3/s. What is the probability it has left

Question:

A molecule leaves a cell at rate λ = 0.3/s. What is the probability it has left by the end of the third second? By the end of the first millisecond? Compare your last answer with the definition of rate.
Find the probabilities of the above events. Find the associated p.d.f., c.d.f., and survivorship function, and give the expectation and variance.