Suppose that the p.d.f. of the life (in weeks) of a certain part is f(x)=3x^2/(400^3), 0<400/
A) Graph the p.d.f and show that the probability of the part failing in the first 200 weeks is 1/8
B)To decrease this probability, four independent part are placed in parallel so that all must fail if the system is to fail. Show that the p.d.f of the life y of this parallel system is g(y)=12y^11/(400)^12, 0<400.