(11) the integrating factor for the given de is (a)e* (b)* x'e (c) xe'; (d) ex; (e) none of these. (12) the general solution of the given de is y = (a) e/x2 +c/(x'e); (b) e/(2x)+ c/(xe); (c)* e/(2x)+ (d) e/(2x-)c/xe); (e) none of these 2x given: + kxy4-2x) dx + (3xy2 + 20xy) dy-0 (13) the value of k so that the above de is exact is 2 (a) 0; (b) 1; (c) 5; (d)* 10; (e) none of these.