Q₁ and Q₂ are point charges located at (0, -4, 3) and (0, 1, 1) respectively. If Q₁ = 2nC, find Q₂ such that:
a. The force on a test charge at (0, -3, 4) has no z component.
b. E (electric field) at (0, -3, 4) has no y component.