B: Graphs of vector valued functions can range from continuous and smooth to discontinuous and wildly erratic. A curve r(t) is smoothly parametrized by r(t), or that r(t) is a smooth function of t if r' (t) is continuous and r' (t) = 0 for any allowable value of t. Geometrically, this means that a smoothly parametrized curve can have no abrupt changes in direction as the parameter increases. Determine whether the following vector valued functions are smooth. a) r(t) = a costi + asint j + ct k; a&c> 0 b) r(t) = t²i+t³j