The function f(x) is defined as follows: f(x) = 2+x if x >=0 , f(x) = 2-x if x <= 0 .Then function f(x) at x=0 is: a)continious and differentiable  b) continuos but not differentiable   c)  differentiable but not continous d) neither continous nor differentiable . No links , please give a detailed explaination .