The performance of a file system depends upon the cache hit rate (fraction of blocks found in the cache). If it takes $1\: msec$ to satisfy a request from the cache, but $40\: msec$ to satisfy a request if a disk read is needed, give a formula for the mean time required to satisfy a request if the hit rate is $h.$ Plot this function for values of $h$ varying from $0$ to $1.0.$
