Let \( f:[0,\infty)\to [0,3] \) be a function defined by Then which of the following is true?
\( f \) is continuous everywhere but not differentiable exactly at two points in \( (0,\infty) \)
\( f \) is not continuous exactly at two points in \( (0,\infty) \)
\( f \) is differentiable everywhere in \( (0,\infty) \)
\( f \) is continuous everywhere but not differentiable exactly at one point in \( (0,\infty) \)