The town of Langley does not have any public snowplows. Anyone who wants their street cleared of snow must hire a private snowplow company to do it for $90. Mike, Chris, and Sarah all live on a dead-end street, with Sarah living at the very end of it. Mike and Chris each values snow removal at $50, while Sarah values it at $70. What is an efficient (social welfare maximizing) solution to this problem? (2 marks) What problems can occur when trying to enact this solution? (1 mark)