A records collector has r distinguishable records of pop genre and w distinguishable records of rock genre; after putting on a blindfold the collector lines up the records in her collection at random, so that each ordering of the records is assumed equally likely.

(a) Describe the sample space and compute its cardinality in terms of r and w.

(b) Compute the probability that the record in the ith position, 1 i r + w, is a record of pop genre.