A block of mass $$m$$ is placed on a surface having vertical cross section given by $$y = \frac{x^2}{4}$$. If coefficient of friction is 0.5, the maximum height above the ground at which block can be placed without slipping is:

A

$$\frac{1}{4}$$ m

B

$$\frac{1}{2}$$ m

C

$$\frac{1}{6}$$ m

D

$$\frac{1}{3}$$ m