For a bayes network a < - b -> c where the variables are boolean. complete the following cpts so that p(a=t, b=t, c=t)=1/18, and p(a=f, b=f, c=f)=1/24: p(b=t)=? p(a=t|b=t)=?

p(a=t|b=f)=1/2
p(c=t|b=t)=1/4
p(c=t|b=f)=3/4

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?