(define (sum term a next b)
        (define (iter a  result)
                (if (> a b)
                        result
                        (iter (next a) (+ result (term a)))))
        (iter a 0))


(define (cube x) (* x x x))


(define (next x) (+ x 1))

(define (sum-cube a b)
        (sum cube a next b))