(1) Find the defective products proportionality: (2*0.1) : (3*0.2) : (4*0.1) --> 0.2 : 0.6 : 0.4

(2) Now you know that the most probable machine isY, 50% of all defective products are produced byY.

(3) The probability thatXproduced the given defective bullet is 0.2/(0.2+0.6+0.4)=1/6