Ex-1.33

(define (filtered-accumulate filter combiner
                              null-value term a next b)
   (cond ((> a b) null-value)
         ((filter a)
          (combiner (term a)
                    (filtered-accumulate filter combiner
                                         null-value term
                                         (next a) next b)))
         (else
          (filtered-accumulate filter combiner null-value
                               term (next a) next b))))
;a
(define (incf i) (+ i 1))
(define (sum-sq-prime-nums a b)
  (filtered-accumulate prime? + 0 square a incf b))

;b
(define (return-arg arg) arg)
(define (prod-nums-lt-n n)
  (define (relative-prime? x)
    (if (> (gcd x n) 1) #f #t))
  (filtered-accumulate relative-prime? * 1
                       return-arg 1 incf n))