Use the fact that the expected value of an event is a probability weighted average, the sum of each possible outcome multiplied by the probability of the event occurring.
You own a house worth $\$ 400,000$ that is located on a river. If the river floods moderately, the house will be completely destroyed. This happens about once every 50 years. If you build a seawall, the river would have to flood heavily to destroy your house, which happens only about once every 200 years. What would be the annual premium for an insurance policy that offers full insurance? For a policy that pays only $75 \%$ of the home value, what are your expected costs with and without a seawall? Do the different policies provide an incentive to be safer (i.e., to build the seawall)?