Statistics and Probability

they've identified mr.bottle snaps a potential candidate to claim and start mining. the probability Of funding gold at mt.bottlesnaap is 20%, silver is 50%, and a dragon is 30%

if a local insurance salesperson offered to sell the dwarves an insurance policy that would pay the dragon it's non-eating money should the mountain be home to a dragon (thus not allowing the dwarves to havr to pay 80 gold if there's a dragon there) what is the most that the band of dwarves could pay and still break even on the insurance policy given the expected cost?