Question 1150678
0.05 probability absent and 0.95 probability present


probability at most is 13 is 1- probably (14 or 15) are there
that second term is 15C14*0.95^14*0.05=0.3658 plus 15C15*0.95^15=0.4633
They add to 0.8290 (rounding at end)
probability overall of 13 or fewer is 1-0.8290=0.1710 ANSWER


probability of 12 attending is 15C12*0.95^12*0.05^3=0.0307
probability of 13 attending is 0.1348

0.0307
0.1348
0.3658
0.4633

Given that 12 attend, what is the probability it will be 14 or 15, is another way to phrase b.
That would be their sum over the sum of p(13,14,15)
0.8290/0.9638=0.8601