A large fruit-eating bat called the black flying fox, Pteropus alecto, occupies a large mangrove swamp on Indooroopilly Island. Assume that80% of these bats are infected with an ectoparasitic mite and 30% have larger tick parasites. Twenty percent are infected with both.

Find the probability that a randomly chosen bat will have some parasites (mites or ticks).

If a randomly chosen bat has mites, what is the probability that it will not have ticks?