Jack and Jill are the only two residents in a neighborhood, and they would like to hire a security guard. The value of a security guard is $50 per month to Jack and $90 per month to Jill. Irrespective of who pays the guard, the guard will protect the entire neighborhood and charge $120 per month for the service.Suppose Jack earns $4,000 per month and Jill earns $8,000 per month. a. With a proportional tax of 1 percent on income, how much would Jack and Jill pay, and would it be enough to pay for the security guard?

This is a form of non-rival service that does not get reduced by consumption by one of the parties. The security guard protects the entire neighbourhood.

Also it is a non-excludable service. If one party does not pay he will still enjoy the service.

Based on their income information and the fact that they are taxed 1%

Jack will pay 0.01 * 4,000 = $40

Jill will pay 0.01 * 8,000 = $80

The total sum is 40 + 80 = $120

As the security guard requires $120 to do the job, their contribution is sufficient.

However the value to Jack is $50 and he pays $40 so he has an excess value of $10

Jill gets a value of $90 but pays $80, so she gets an excess value of $10