Which of the following fringe benefits is taxable to the employee receiving the benefit?

a$.$ A $20\%$ discount on clothing to a department store employee on which the store makes a

b$.$ A $15\%$ discount on a building sold to an employee of the developer

c$.$ Reimbursement of laser eye surgery cost to an employee who has a flexible medical spen

d$.$ A term paper typed and copied by a company secretary for another employee