Mahler PE4.12

If I use the formula in ASM Chp 49 (Bernoulli/beta), then

a*=a+k=3+5=8
b*=b+n-k=3+6-5=4

q=a*/(a*+b*)=2/3

Pr(5 boys and 1 girl)=6*(q^5)*(1-q)=0.2634

Do you know why I can't use the formula above?

Thanks in advance!!!


Mahler PE4.12