Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
1940 UK & Ireland Greyhound Racing Year
Table title:
Tracks opened
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Date </th><th colspan=1 rowspan=1 > Stadium/Track </th><th colspan=1 rowspan=1 > Location </th></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 23 March </td><td class="highlighted"  colspan=1 rowspan=1 > Sunderland Greyhound Stadium </td><td colspan=1 rowspan=1 > Sunderland </td></tr>
<tr> <td colspan=1 rowspan=1 > 1 April </td><td colspan=1 rowspan=1 > Mains Park </td><td colspan=1 rowspan=1 > Linlithgow </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 11 May </td><td class="highlighted"  colspan=1 rowspan=1 > Yarmouth Stadium </td><td colspan=1 rowspan=1 > Yarmouth </td></tr>
</table>
Question:
On what dates did Sunderland Greyhound Stadium and Yarmouth Stadium open?
Answer:
Sunderland Greyhound Stadium opened on 23 March and Yarmouth Stadium opened on 11 May.