package main

import (
  "errors"
  "fmt"
)

var (
  ErrHourlyRate  = errors.New("invalid hourly rate")
  ErrHoursWorked = errors.New("invalid hours worked per week")
)

func main() {

  pay, err := payDay(81, 50)
  if err != nil {
    fmt.Println(err)
  }

  pay, err = payDay(80, 5)
  if err != nil {
    fmt.Println(err)
  }

  pay, err = payDay(80, 50)
  if err != nil {
    fmt.Println(err)
  }

  fmt.Println(pay)

}

func payDay(hoursWorked, hourlyRate int) (int, error) {

  if hourlyRate < 10 || hourlyRate > 75 {
    return 0, ErrHourlyRate
  }
  if hoursWorked < 0 || hoursWorked > 80 {
    return 0, ErrHoursWorked
  }

  if hoursWorked > 40 {
    hoursOver := hoursWorked - 40
    overTime := hoursOver * 2
    regularPay := 40 * hourlyRate
    return regularPay + overTime, nil
  }

  return hoursWorked * hourlyRate, nil

}