The mean life of a certain computer hard disk in continual use is 7 years.

(a) How long a warranty should be offered if the vendor wants to ensure that not more than 27 percent of the hard disks will fail within the warranty period? (Round your intermediate values to 4 decimal places and final answer to 4 decimal places.)

Period of warranty years  

(b) How long a warranty should be offered if the vendor wants to ensure that not more than 47 percent of the hard disks will fail within the warranty period? (Round your intermediate values to 4 decimal places and final answer to 4 decimal places.)

Period of warranty years