11. A certain power series ) an(I -4)" converges when r = 1 and diverges when r = 13. Which n=1 of the following could be the radius of convergence of this series? (a) 2 (b) 3 (c 9 (d)Two of the above (e) none of these lego (d) 12. What is the limit of the sequence In n In(n2 + 1) ) =1 ? (a) o (b) _ 2 (c) 1 (d) The sequence diverges to infinity ed suidelor d bankeddo biloe add ed e fal or (e) none of these lo similov adl elmoanger lads Lengesal ade acoolto see and atd 13. Find the interval of convergence of the series: (2x - 1) 1=1 (50 ) n (a) -2