;;
;; FILE:     homework03.rkt
;; AUTHOR:   [ YOUR NAME HERE ]
;; DATE:     [ YOUR DATE HERE ]
;; COMMENT:  Includes rackunit tests for the examples in the assignment.
;;
;; MODIFIED: 
;; CHANGE:   
;;

#lang racket
(require rackunit)

; -----   [1]   -----

(define price-per-ounce-for
  (lambda (units-per-pack ounces-per-unit)
    'YOUR-CODE-HERE ))

(define big-bottles-at (price-per-ounce-for 6 24))
(check-= ((price-per-ounce-for 6 16.9) 1.44) 0.01420118 0.0001)
(check-= (big-bottles-at 1.44) 0.01 0.0001)

; -----   [2]   -----

(define circle-area
  (lambda (r)
    (* pi (expt r 2))))

(define ring-area-around
  (lambda (inner)
    'YOUR-CODE-HERE ))

(define area-for-2inch-bolt (ring-area-around 2))
(check-= ((ring-area-around 1) 2)  9.42477796076938 0.0001)
(check-= (area-for-2inch-bolt 5)  65.97344572538566 0.0001)

; -----   [3]   -----

(define average-weight
  (lambda (height-weight-list)
    'YOUR-CODE-HERE ))

(define average               ; a helper function
  (lambda numbers
    (/ (apply + numbers)
       (length numbers))))

(check-= (average-weight '((79 . 225))) 225.0 0.0001)
(check-= (average-weight '((70 . 150) (62 . 100))) 125.0 0.0001)

; -----   [4]   -----

(define total-margin
  (lambda (list-of-pairs)
    'YOUR-CODE-HERE ))

(define uni-women
  '((102 51) (78 67) (53 94) (64 75) (54 71) (64 68)
    (65 84) (62 115) (59 78) (70 87) (52 54) (82 52)
    (85 79) (76 52) (95 75) (67 72) (77 88) (105 59)))

(check-equal? (total-margin '((102 51) (78 67) (53 94)))
              103)
(check-equal? (total-margin uni-women)
              387)

; -----   [5]   -----

(define min-open-seats
  (lambda (sections)
    'YOUR-CODE-HERE ))

(define example '(("Dept" "Number" "Section" "Class Nbr" "Capacity" "Enrolled")
                  ("CS" "1000" "1" "11546" "30" "30")
                  ("CS" "1025" "1" "11547" "30" "30")
                  ("CS" "1120" "1" "11557" "30" "15")
                  ("CS" "1130" "1" "11548" "30" "18")))
(check-equal? (min-open-seats example) 0)

; -----   end   -----