Let $\;f(n)=[\large\frac{1}{3} + \large\frac{3n}{100}]n\;$ , where [n] denotes the greatest integer less than or equal to n .Then $\;\sum_{n=1}^{56} f(n)\;$ is equal to :

Question

$(a)\;56\qquad(b)\;689\qquad(c)\;1287\qquad(d)\;1399$