(a)

The integral is .

The integral represents probability of the lifetime of the car tire.

The probability density function : .

.

The expression represents the probability of a randomly chosen tire which will have a lifetime between  and miles.

(b)

The integral is .

The integral represents probability of the lifetime of the car tire.

.

The above expression represents that the probability that a randomly chosen tire will have a lifetime of at least miles.

(a) The probability that a randomly chosen tire will have a lifetime between   and miles.

(b) The probability that a randomly chosen tire will have a lifetime of at least miles.