The differential equation 2 bx [a y sin(5x) + 2e³× cos(4 y) +mx²] dx + [cos(cx) + 2e³ * sin(4y)] dy = 0 cos(4y)+mx ☐ b= c=5, many is exact for a = −5, b = −4, c = 5, m any real is exact for a = -5, b = 5, c = -4, m any real ☐ is exact for b = -4, c = 5 and any reals a, m О is exact for a = -5, b b = −4, c = 5, m = 0 only ☐ is never exact