If the estate should not be sufficient to cover all the legacies or devises, their payment shall be made in the following order:
(1) Remuneratory legacies or devises;
(2) Legacies or devises declared by the testator to be preferential;
(3) Legacies for support;
(4) Legacies for education;
(5) Legacies or devises of a specific, determinate thing which forms a part of the estate;
(6) All others pro rata. (887a)