Let x0, x1,.....xn.... be a sequence of independent and identically distributed continuosu random variables and let W be the "waiting time" until the first recrd value of the sequence is attained. That is, W is the random variable, taking its values in N, which is specified by

{W = n} <=> {(xj <= x0, for all j is an element of { 1,2,....(n-1)}) and (xn> x0)}

Show that, for any n is an element of N,

P[W=n] = 1/(n(n+1))

Any help with these sort of questions would be helpful, even if its jsut a book that gives good examples!