PLEASE HELP

Question 1) Five percent of a certain grade of tires wear out before 20,000 miles, and another 5 percent of tires exceed 30,000 miles. It is known that wearout is normally distributed. a) Find the MTTF. b} Using basic calculations, it is easy to show that o = 3,039.5 miles (show it to yourself). Determine the tire reliability at 22,000 miles