The government is thinking about constructing flood defences beside a river. It has worked out the costs and benefits as shown: costs $m private 450 external 60; benefits $m private 260 external 190. Using cost-benefit analysis, which decision about flood defences, together with the reason for it, is correct?
- Abuild; external benefits are greater than external costs
- Bbuild; social benefits are greater than private benefits
- Cdo not build; private costs are greater than the external benefits
- Ddo not build; social costs are greater than the social benefits