Procedural representation of pairs

Here is an alternative procedural representation of pairs. For this representation, verify that (car (cons x y)) yields x for any objects x and y .

(define (cons x y)
  (lambda (m) (m x y)))

(define (car z)
  (z (lambda (p q) p)))

What is the corresponding definition of cdr ? (Hint: To verify that this works, make use of the substitution model of section 1.1.5.)

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