"Why Are Protocols Useful?" section missing Teacher's Notes

import Foundation

enum EmployeeType {
    case Manager
    case NotManager
}

class Employee {

    let name: String
    let address: String
    let startDate: NSDate
    let type: EmployeeType

    var department: String?
    var reportsTo: String?

    init(fullName: String, employeeAddress: String, employeeStartDate: NSDate, employeeType: EmployeeType) {
        self.name = fullName
        self.address = employeeAddress
        self.startDate = employeeStartDate
        self.type = employeeType

    }

    func pay() -> (basePay: Double, benefits: Double, deductions: Double, vacationTime: Int) {
        return (0, 0, 0, 0)
    }

}

func payEmployee (employee: Employee) {
    let paycheck = employee.pay()
}

class HourlyEmployee: Employee {
    var hourlyWage: Double = 15.00
    var hoursWorked: Double = 0
    let availableVacation = 0

    override func pay() -> (basePay: Double, benefits: Double, deductions: Double, vacationTime: Int) {
        return (hourlyWage * hoursWorked, 0, 0, availableVacation)
    }
}