Let Xt be equal to the number of particles emitted from a radioactive source during a time interval of length t. Assume that Xt has a Poisson distribution with parameter t. A counting device is set up to keep count of the number of particles emitted. Suppose that there is a constant probability p that any emitted particle is not counted. If Rt equals the number of particles counted during the specified interval, what is the probability distribution of Rt?