S ◦ R : duplicate relations?

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$R$ = $\{(2,1),(2,2)\}$

$S$ = $\{(1,2),(2,2)\}$

$S \circ R$ = {(2,2),(2,2)}

Is the answer then {(2,2),(2,2)} or {(2,2)} I couldn't find anything about removing duplicates relations, but it makes more sense that way. Especially when put in a matrix.

Unless this is allowed

$S \circ R$ = $\begin{bmatrix} 0 & 0 \\ 0 & 2 \\ \end{bmatrix}$