Displaying Transaction Id in Thank you letter

<table>
	<thead>
		<tr>
			<th>Date</th>
			<th>Sum Recieved</th>
			<th>Payment Method</th>
			<th>Receipt Number</th>
		</tr>
	</thead>
	<tbody>
		<tr>
			<td>{contribution.receive_date}</td>
			<td>{contribution.total_amount}</td>
			<td>{contribution.payment_instrument}</td>
			<td>
				{capture assign=temp}
					{contribution.trxn_id}
				{/capture}
				{if $temp ne ""}
					{$temp}
				{else}
					{contribution.check_number}
				{/if}
			</td>
		</tr>
	</tbody>
</table>