Lead in metal shredder residue. On the basis of data collected from metal shredders across the nation, the amount x of extractable lead in metal shredder residue has an approximate exponential distribution with mean u = 2.5 milligrams per liter (Florida Shredder’s Association).

a. Find the probability that x is greater than 3 milligrams per liter.

b. Find the probability that x is less than 6 milligrams per liter.