LISP Cube List Function

WITHOUT USING LET

(defun cube-list (lst)

         (cond ((null lst) nil)
                   (t ( cons (* (car lst) (car lst) (car lst)) (cube-list(cdr lst)) ) )

         )
)

USING LET

(defun cube-list (lst)
         (cond ((null lst) nil)
                   (t ( let ((a (car lst))) (cons (* a a a) (cube-list(cdr lst))) ) )
         )
)