Suppose there are two types of persons: high-ability and low-ability. each year of schooling costs a high-ability person $10,000 and costs a low-ability person $20,000. firms wish to use education as a signaling device where they intend to pay $60,000 to workers without a minimum required amount of schooling and $100,000 to those who meet this requirement. what would be the range of years of schooling that firms would have to require in order for there to be a separating equilibrium?