C 1 is the number of remaining flies, A 1 is the different ways to fly out, C2 is the last way to fly out, A2 is the way to jump in line with another fly among the flies, C3 is the way to choose ζ flying out of 8 flies, and A3 is all the ways to fly out of the selected flies (C is the combination number and A is the arrangement number).
Example: p (zeta = 0) = (6c0 * 6a6 * 2c1* 7a1)/(8c8 * 8a8) = 7/28.
p(ξ= 1)=(6c 1 * 5 a5 * 2c 1 * 6a 1)/(8c 7 * 7a 7)= 6/28
p(ζ= 4)=(6 C4 * 2 a2 * 2c 1 * 3a 1)/(8 C4 * 4a 4)= 3/28
p(ξ= 6)=(6c 6 * 0a 0 * 2c 1 * 0a 0)/(8c 6 * 2 a2)= 1/28
He can be included in the distribution list.
(2) The expected value is calculated by the formula of distribution list.
(3) probability p (zeta ≥ e zeta) = p (zeta ≥ 2) = (5+4+3+2+1)/28 =15/28.