Okay, so the answer for the first two questions are...

A:

E(Q) = n * p , where n are number of trials and p is probability...

When n is unknown and E(Q) is 6 and p is 0,04, then

n = 6/0,04 = 150.

B:

X1 = 50 and X2 = 50, so Y = x1 + x2 = 100, so n = 100.

Var(Y) = n * p * q , where n are number of trials, p is probability and q is (1 - p)

Var(Y) = 100 * 0,04 (1 - 0,04) = 3,84.

and

E(Y) = n * p = 100 * 0,04 = 4.

I'm however still having trouble with the next questions...

I tried to put up a binomial distribution two answer C, but as the answer is supposed to be 0.785, it doesn't match my answer of 0,78837. So it is probably wrong... Any ideas?

Follow-up:

The answer is...

P(Y<=5) = SUM from k = 0 to 5 of ( (100*0,04)^k / k! ) * exp(-100*0,04) = 0,78513.

and the answer for the last question is .322..?