I require a detailed solution for this question.

Suppose all blocks of data on a rotating disk begin at a sector
boundary.  There is one read/write head.  Suppose that read/write
requests arrive at the head as a Poisson process with parameter landa,
requiring blocks of data of fixed length b sectors, beginning at a
random sector boundary.  Assume that the disk spins at a rate of r
revolutions per second and has s sectors.  Also, assume that a request
always find the head at aboundary between two sectors.  What is the
mean queue length and mean waiting time for a disk access?