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 (define (RLC R L C dt) 
         (define (rcl vc0 il0) 
                 (define vc (integral (delay dvc) vc0  dt)) 
                 (define il (integral (delay dil) il0 dt)) 
                 (define dvc (scale-stream il (- (/ 1 C)))) 
                 (define dil (add-streams (scale-stream vc (/ 1 L)) 
                                                                 (scale-stream il (- (/ R L))))) 
                 (define (merge-stream s1 s2) 
                         (cons-stream (cons (stream-car s1) (stream-car s2)) 
                                                  (merge-stream (stream-cdr s1) (stream-cdr s2)))) 
                 (merge-stream vc il)) 

why not simply (cons vc il) at the end of the procedure instead of merging? the exercise says "a pair of the streams".