;datos
;hora inicial
;hora final

(define(contrato hi hf)
  (cond
    [(and(>= hi 0)(<= hf 10))(* 25 (- hf hi))]
    [(and(> hi 10)(<= hf 16))(+(* 25 (- hf hi))(* 28 (- hf hi)))]
    [(and(> hi 16)(<= hf 10))(+(* 25 (- hf hi))(* 28 (- hf hi))(* 10 (- hf hi)))]
    [else(error "Hola")]


    ))

(contrato 0 19)