;; constants
(define hourly-rate 12)


;; tax : number -> number
;; Example (tax 120) -> 0
;; Example (tax 350) -> 52.5
;; Example (tax 700) -> 196
(define (tax pay)
  (cond
    [(<= pay 240) 0]
    [(<= pay 480) (tax-owed pay 15.0)]
    [(> pay 480) (tax-owed pay 28.0)]))

    
;; tax-owed : number number -> number
(define (tax-owed pay rate)
  (* (/ rate 100) pay))


;; netpay : number -> number
;; Example (netpay 15) -> 180
;; Example (netpay 35) -> 255
;; Example (netpay 70) -> 604.80
(define (netpay hours)
  (- (gross-pay hours) (tax (gross-pay hours))))


;; gross-pay : number -> number
(define (gross-pay hours)
  (* hours hourly-rate))