(a) Which rule above justifies the following calculations? (Just name which Rule)

𝒪⊕𝒪 = 𝒪; 𝒪⊕(1, 1) = (1, 1); 𝒪⊕ (1,6)= (1,6); 𝒪⊕(3,0) = (3,0); 𝒪⊕(5, 1) = (5, 1); 𝒪⊕(5, 6) = (5, 6)

(b) Which rule above justifies the following calculations? (Just name which Rule)

(1, 1)⊕ (1,6)= 𝒪; (3,0)⊕ (3,0) = 𝒪; (5, 1)⊕ (5, 6) =𝒪.