Mathematics

Problem

Let

f(x)=\lfloor x \rfloor + |x-1|

for all real

x

, where

\lfloor x \rfloor

denotes the greatest integer less than or equal to

x

. In the open interval

(0,4)

, the number of points at which

f

is not differentiable is a) 4 b) 3 c) 2 d) infinitely many