$\int \limits_0^n \{x\} dx = \int \limits_0^n x-[x]dx=\large\frac{n}{2}$ if $n=2$ then $y=?$

Question

$$\begin {array} {1 1} (a)\;n \\ (b)\;\frac{n}{2} \\ (c)\;n^2 \\ (d)\;\frac{n}{2} \end {array}$$