Let \( f:[0,\infty)\rightarrow [0,\infty) \) be defined as \( f(x)=\displaystyle\int\limits_{0}^{x}[ y]r \,dy \), where \( [ x] \) is the greatest integer less than or equal to \( x \). Which of the following is true?
\( f \) is continuous at every point in \( [0,\infty) \) and differentiable except at the integer points
\( f \) is continuous everywhere except at the integer points in \( [0,\infty) \)
\( f \) is both continuous and differentiable except at the integer points in \( [0,\infty) \)
\( f \) is differentiable at every point in \( [0,\infty) \)