For workers in Group H (high-skill workers), the cost of attaining an educational level y is $C_H(y) = \$10y$; for workers in Group L (low-skill workers), the cost of attaining an educational level y is $C_L(y) = \$15y$.
Employees will be offered \$60 if they have $y \ge y^*$, where $y^*$ is an educational threshold determined by the employer. They will be offered \$20 if they have $y < y^*$.
a) Find if in equilibrium, education can be used as a market signal of the worker's skill.
b) Find the range for which education can be used as a market signal of the worker's skill (the solution is a range such as $5 \ge y^* \ge 1$)