lab1

(define SHEEP .)
(define SCENE (empty-scene 500 500))
(define CAR .)
(define BALLOON .)
(define CAKE .)

;;Exercise 3
(define (letter-grade score)
  (if (> score 90) "A"
      (if (> score 80) "B"
          (if (> score 70) "C"
              (if (> score 60) "D" "F")))))
;;Exercise 4
(define (how-long min)
  (if (< min 10) "Great!"
      (if (<= min 60) "Okay" "Not Good")))

;;Exercise 5
(define (good-weather str)
  (if (equal? str "sunny") true false))

;;Exercise 6
(define (str-len str)
  (if (< (string-length str) 3) "stubby"
      (if (< (string-length str) 11) "shorty"
          (if (< (string-length str) 26) "middling" "too wordy"))))

;;Exercise 7
(define (sale wish)
  (cond [(equal? wish "car")(place-image CAR 200 200 SCENE)]
    [(equal? wish "balloon") (place-image BALLOON 200 200 SCENE)]
    [(equal? wish "cake") (place-image CAKE 200 200 SCENE)]
    [else (text "Sorry, wish for something else" 20 "olive")]))

;;Exercise 8
(define (draw-sheep x)
  (place-image SHEEP x 200 SCENE))

;;Exercise 9
(define (on-top img1 img2)
  (overlay/align "left" "top" img1 img2))