For what value of k the given differential equation is exact? -(3x+y - 3e4x)dy = (3kye¹x + 6x³y²)dx. Select one: Ok = -2 Ok = 2 None of these. Ok = 4 Ok=-4 Question [5 points]: The DE: 8 (3x² + -sin xy) dx = -N(x, y)dy x is an exact differential equation if N(x, y) is equal to. Select one: O N(x, y) = 3x² + ○ N(x, y) = 6y + cos xy None of these. ○ N(x, y) = y²-cos xy O N(x, y) = 3y² + sin xy sin xy The differential equation is Select one: Bernoulli None of the others O separable exact linear y' - 10xe¹ = 0 An integrating factor u(x) for the linear differential equation xy' - 4y = x² + 1 is Select one: Ox³ O None of the others O ex