Which one of the following statements is correct?
1
The marginal cost of providing a private good to an additional individual is always positive, while that of public good is zero.
2
The marginal cost of providing a public good to an additional individual is always negative, while that of private good is positive.
3
The marginal cost of providing a public good to an additional individual is always zero, while that of private good is negative.
4
The marginal costs of providing both, a public good and a private good, to an additional individual are always zero.