Solve this please

. Both continuity, differentiability, and s-differentiability are desirable properties for a function to have. (a) Show that if f is differentiable at a point a, then it is *differentiable at a. In such a case (D * f)(a,) = 2f(o,) f'(a). (b) Prove or disprove: \"if f is *differentiable at a, then it is differentiable at a\". (c) Show that if f is *-differentiable at a, then f2 is continuous at a. Is the converse statement true? Justify your answer. ((1) Prove or disprove: \"if f is *-differentiable at a, then f is continuous at a