Question 4 Let B : R3 - R3 be the vector field defined by B(x, y, =) = (fi(x) +xz, f2(y) + yz, fa(=)) where f1, f2, and fa are any single-variable functions. (4A) What is curl B? (4B) Let [ be the curve formed by the intersection of the sphere a* +y'+ 2 = 36 with the plane = = 3, oriented positively when viewed from the extreme positive z-axis. Calculate [ B - Tds