These are some homework questions I'm having trouble with.

1.A team is formed from selecting eight Americans and two Canadians. What is the minimum team size that guarantees at least a 90% probability that the team will not be composed of Americans only.

I'm really lost with this question.

2. Two brands of painkillers are on the market: A and B. One in four hundred people taking A suffer from side effects, and one in 1200 people taking B suffer from side effects. It is estimated that equal numbers of people take each kind of drug. If A is taken off the market, show that the probability of side effects will be halved.

I have this, but I'm doing something wrong.

P(A or B) = P(A) + P(B)

= 1/400 + 1/1200

=3/1200 + 1/200

=4/1200

=1/300

A is taken off the market.

1/1200 + 3/1200

= 4/2400

=1/600