Trade receivables as at $1$st April $2020$ were $382,400.$ During the year ended $31$st March $2021,$ Sales and Sales Returns amounted to $859,600$ and $18,400$ respectively; while $659,800$ was received from credit customers and $8,200$ was written off as a bad debt. An allowance for doubtful debts is maintained at $4\%$ of debts outstanding. Calculate the expenditure written off in the year to $31$ March $2021.$