Question 665650
I'm not an expert on this, but I'll give you an answer and maybe one of the other tutors can comment/correct it.
I say that the
(1) P(at least one writes) = 1 - P(none write) or
(2) P(at least one writes) = 1 - (3/10)(2/9)(1/8)
(3) P(at least one writes) = 119/120
The
(4) P(at least one doesn't write) = 1 - P(all write)
(5)    ditto                      = 1 - (7/10)(6/9)...(1/4)
(6) P(at least one doesn't write) = 119/120
Sorry, no guarantees.