(a) The random variable Dn in Section 2.7.4 was defined as the initial string length of encoded bits required to decode the first n symbols of the source input. For the run-length coding example in Exercise 2.23, list the input strings and corresponding encoded output strings that must be inspected to decode the first source letter, and from this find the pmf function of D1.
(b) Find the pmf of D2. One point of this exercise is to convince you that Dn is a useful rv for proving theorems, but not an rv that is useful for detailed computation. It also shows clearly that Dn can depend on more than the first n source letters.