Under average driving conditions, the life lengths of automobile tires of a certain brand are found to follow an exponential distribution, with a mean of 30,000 miles. Find the probability that one of these tires, bought today, will last the following number of miles
A-Over 30,000 miles
B-Over 30,000 miles, given that it already has gone 15,000 miles (note this is asking if the tires will go over the 30,000 mark which is different than asking if they will go another 30,000 miles).