If f(x)= \{\table\frac{1}{2} (b^2-a^2) \text{,}, 0 \leq x \leq a ; \frac{1}{2} b^2-\frac{x^2}{6}-\frac{a^3}{3 x}\text{,}, a< x \leq b; \frac{1}{3} (\frac{b^3-a^3}{x}) \text{,}, x>b

Correct Answer is : f′(x) is not differentiable at x=a

{\f}^{' '}( {\a})= {\b}^2- {\a}^2

{\f}^{'}( {\x}) is not differentiable at {\x}= {\a}