Calculate the molar solubility of the salt A₃B₄, given that Ksp for this salt is 4.91×10⁻¹⁶. Show all calculations.
a) 7.00×10⁻⁶ M
b) 6.21×10⁻⁸ M
c) 2.10×10⁻⁷ M
d) 1.90×10-⁵ M