P(ct|art)=P(ct & art)/P(art)
<=> P(ct & art)=P(ct|art) * P(art)
<=> P(ct & art)=0.0001*0.001= 0.000001

P(ct|~art)=P(ct & ~art)/P(~art)
<=>P(ct & ~art)=P(ct|~art) * P(~art)
<=>P(ct & ~art)= 0.01*(1-0.001)
<=>P(ct & ~art)= 0.00999

Assim: P(ct)=P(ct|art)+P(ct|~art)=0.000001+0.00999=0.009991