the time failure in months X, of the light bulbs produced at two manufacturing plants A and B obey, respectively the following PDFs
for A: Fx(x) = ( 1 - e(-x/5))u(x)
for B: Fx(x) = ( 1 - e(-x/2))u(x)
plants B produced three times as many bulbs as plant A. the bulbs indistinguishable to the eye, are intermingled and sold. What is the probabilty that bulbs purchased random will burn at least.
2 months, 5 months, 7 months
