Final answer:
Given Timmy has decided to take a free-rider approach, he will not contribute any money to the fund for extra police patrols; his contribution is $0.
Step-by-step explanation:
The student asks how much Timmy will contribute to the fund for extra police patrols, given he has chosen to take a free-rider approach. In economics, a free-rider is an individual who benefits from resources, goods, or services without paying for the cost of the benefit. Since Timmy believes he will benefit from the extra patrols without contributing, the amount he will contribute is $0, as free-riders choose not to pay if they can benefit from the service without paying for it.