http://i45.tinypic.com/2wburdd.jpg

member 1 is exponential of lambda=1 X1~exp(3)

member 2 is U(2,4) X2~U(2,4)

member 3 works 3 hours and then dont work at all

X3=1 for t<3

X3=0 for t>3

$\displaystyle

F_{X_{ab}}(t)=P(x_b<t)=p(max(x_1,x_{23})<t)=P(x_1< t)P(x_{23}<t)\\

$

$\displaystyle =P(x_1<t)P(min(x_2,x_{3})<t)$

i developed it at much as i could

i dont know how to continue from this point

to find the formula