#| BEGIN (Write your solution here) |#
(define (attach-tag type-tag contents)
    (cond ((eq? type-tag 'scheme-number) contents)
          (else (cons type-tag contents))
    )
)

(define (type-tag datum)
    (cond ((pair? datum) (car datum))
          ((number? datum) 'scheme-number)
          (else (error "Bad tagged datum: TYPE-TAG" datum))
    )
)

(define (contents datum)
    (cond ((pair? datum) (cdr datum))
              ((number? datum) datum)
              (else (error "Bad tagged datum: CONTENTS" datum))
    )
)