(10 points) If X is negative exponential with parameter A, that is, f(I) = Ne , r > 0. The fractional part of r is defined as {r} = x - (x] with (x] being the largest integer less than or equal to r. For example, [3.1] = 3, and {3.1} =3.1 - [3.1] =0.1. Let Y = {X }, find the p.d.f. of Y