1-2-3.rkt

;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-beginner-reader.ss" "lang")((modname 1-2-3) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
(define (letter fst lst signature-name)
  (string-append
    (opening fst)
    "\n\n"
    (body fst lst)
    "\n\n"
    (closing signature-name)))
 
(define (opening fst)
  (string-append "Dear " fst ","))
 
(define (body fst lst)
  (string-append
   "We have discovered that all people with the" "\n"
   "last name " lst " have won our lottery. So, " "\n"
   fst ", " "hurry and pick up your prize."))
 
(define (closing signature-name)
  (string-append
   "Sincerely,"
   "\n\n"
   signature-name
   "\n"))

(require 2htdp/batch-io)

(define SENSITIVITY 15)

(define (attendees ticket-price)
  (- 120 (* (- ticket-price 5.0) (/ SENSITIVITY 0.1))))

(define (revenue ticket-price)
  (* ticket-price (attendees ticket-price)))

;(define fixedcost 180)

;(define costperattendee .04)

(define fixedcost 0)
(define costperattendee 1.50)

(define (cost ticket-price)
  (+ fixedcost (* costperattendee (attendees ticket-price))))

(define (profit ticket-price)
  (- (revenue ticket-price)
     (cost ticket-price)))

(define (profitv2 price)
  (- (* (+ 120
           (* (/ 15 0.1)
              (- 5.0 price)))
        price)
     (+ 180
        (* 0.04
           (+ 120
              (* (/ 15 0.1)
                 (- 5.0 price)))))))

(profit 1)
(profit 2)
(profit 3)
(profit 4)
(profit 5)