( 1/2 + 1/3 ) x 2/5
c1 = 5/6 x 2/5 = 1/3
c2 = 1/2 x 2/5 + 1/3 x 2/5
= 1/5 + 2/15
= 1/3
3/5 x 17/21 x 2/5
c1 := 17/35 x 2/5 = 34/175
c2 : = (3/5 x 2/5) x 17/21
= 6/25 x 17/21
= 34/175?
( 1/3 - 1/5 ) x 1/2
c1 : = 2/15 x 1/2
= 1/15
c2 : = 1/3 x 1/2 - 1/5 x 1/2
= 1/6 - 1/10
= 1/15