Muzammil M. answered 12/18/22
"Experienced Finance Tutor Seeking Opportunities to Help Students
(a) The security service is a public good for the residents of the estate because it is both non-rival and non-excludable. This means that the benefits of the service cannot be depleted by one individual's use, and it is not possible to exclude certain individuals from enjoying the benefits of the service. In other words, the security service provides benefits to all residents of the estate, regardless of whether they individually contribute to its cost.
(b) Using marginal analysis, we can determine the optimal number of security guards to hire by comparing the marginal cost and marginal benefit of each additional security guard. The marginal cost is the additional cost of hiring one more security guard, while the marginal benefit is the additional benefit that each resident receives from hiring one more security guard.
At the first level of security guards (1 guard), the marginal cost is $150 and the marginal benefit is $10. The marginal benefit exceeds the marginal cost, so it is profitable to hire one more security guard.
At the second level of security guards (2 guards), the marginal cost is $150 and the marginal benefit is $6. The marginal benefit is now less than the marginal cost, so it is not profitable to hire any more security guards.
Therefore, the optimal number of security guards to hire is 2, as this is the point at which the marginal cost equals the marginal benefit.