Final answer:
Singh may have left out the d) non-monetary benefit of buying the pizza.
Step-by-step explanation:
In Singh's cost-benefit analysis of buying a slice of pizza, it seems that he has left out the non-monetary benefit of buying the pizza. While Singh states that there is no monetary benefit, he may not have considered the enjoyment or satisfaction he would get from eating the pizza, which can be a non-monetary benefit. Including this factor would provide a more comprehensive analysis of the costs and benefits.