Consider the vector field F in the figure and the closed circular path C oriented counter-clockwise. (a) Is ? c F . dr positive, negative, or zero? (b) True or False: F = grad f for some function f. Hint: use your answer to part (a). ? (c) Which of the following formulas best fits F? OA. F = ci + yj OB. F = yi - xj (Click on graph to enlarge) Oc. F y (x2 + 72)2 (2+ 72) 2. OD. F = y (x2 + 72)2 i+ (x2 + 2)23