About business probability1

plz help me to solve this problem.

1. The ABC corporation wishes to improve the resistance of its personal computer to disk drve and keyboard failures. At present, the design of the computer is such that disk-drive failures occur only one-third as often as keyboard failures. The probability of simultaneous disk drive and keyboard failures is 0.01.

a) if the computer is 90 percent resistant to disk drive and / or keyboard failures, how low must the disk-drive failures probability be?

b) if the keyboard is improved so thst it fails only twice as often as the dixk-drive(and the simultaneous failure probability is still 0.01),will the disk-drivefailure probability from part (a) yield a resistance to disk-drive and/or keyboard failure higher or lower than 90 percent?