An acid (X) reacts with a base (Y) to produce Mg₃(PO₄)₂. What are X and Y?

a) X = HPO₂; Y = Mg(OH)₂
b) X = H₃PO₄; Y = Mg(OH)₂
c) X = H₃PO₄; Y = Ca(OH)₂
d) X = H₃PO₃; Y = Ca(OH)₂