#lang racket
;; Starter code for A3Q2
;; May contain Unicode characters - download, don't cut/paste from browser
;; You must replace the ? with correct proof terms.

(define answer1 '(? : ((A -> B) -> ((¬ B) -> (¬ A)))))

(define answer2 '(? : ((¬ (A ∨ B)) -> (A -> B))))

(define answer3 '(? : ((A -> (B ∨ C)) -> ((¬ B) -> ((¬ C) -> (¬ A))))))

(define answer4 '(? : ((¬ (A ∨ B)) -> ((¬ A) ∧ (¬ B)))))