Let X] and X2 have the joint pdf fx, x, (1, 12) = e $1-2 for 0

Let Xl and X2 have the joint pdf , = for O < < DO, and O < < DO, and zero elsewhere. What is the joint pdf of Yl Xl and Y2=X2+X1. (I) fyY2 (Yl,Y2) = for O < < < DO. (II) fYl,Y2 (Yl,Y2) = for O < < 00 and O < DO. (Ill) fyY2 (Yl,Y2) = for O < < < DO. (IV) fYl,Y2 (Yl,Y2) eY2 < 00 and O < Y2 < DC. O (III)