7. Suppose that after 10 years of service, 40% of computers have problems with motherboards (MB), 30% have problems with hard drives (HD), and 15% have problems with both MB and HD. What is the...

7. Suppose that after 10 years of service, 40% of computers have problems with
motherboards (MB), 30% have problems with hard drives (HD), and 15% have problems
with both MB and HD. What is the probability that a 10-year old computer still has fully
functioning MB and HD?