Philip is an average contractor in town, and he earns $40,000 a year. Billy is the best contractor in town, and he earns $480,000 a year. Philip's contracting services a. are valued more by the market relative to Billy's and that explains why his income is higher than Billy's. O b. are valued less by the market relative to Billy's and that explains why his income is higher than Billy's. O c. are valued less by the market relative to Billy's and that explains why his income is lower than Billy's. O d. are more expensive because he receives a compensating differential. O