\(\sum\limits_{r =1}^n r^2 - \sum\limits_{m = 1}^n \sum\limits_{r =1}^m r\) is equal to
(a) \(\frac12\left(\sum\limits_{r=1}^n r^2 + \sum\limits_{r = 1}^n r\right)\)
(b) \(\frac12\left(\sum\limits_{r=1}^n r^2 - \sum\limits_{r = 1}^n r\right)\)
(c) 0
(d) None of these