Use the following to answer the given question

Creditors Control Account:
\(\begin{array}{c|c} & & & N \\ \hline Bank & \text{"X"} & \text{Balanxe b/d} & 1,200 \\ Discount & 30 & \text{"Y"} & 1,800 \\ \text{Balance c/d} & 450 & & \\ \hline & & & & \hline \end{array}\)

"Y" represents

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