(define num-sixes ; number of 6's in (lambda (n) ; decimal representation of n (cond ((< n 0) (num-sixes (- n))) ((= n 0) 0) ((= (remainder n 10) 6) (+ 1 (num-sixes (quotient n 10)))) (else (num-sixes (quotient n 10)))))) (define num-odds ; number of odd digits (lambda (n) ; in decimal representation of n (cond ((< n 0) (num-odds (- n))) ((= n 0) 0) ((odd? (remainder n 10)) (+ 1 (num-odds (quotient n 10)))) (else (num-odds (quotient n 10))))))