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:
Douglas John Bell
Table title:
List of aerial victories
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > No. </th><th colspan=1 rowspan=1 > Date/Time </th><th colspan=1 rowspan=1 > Aircraft/ Serial No. </th><th colspan=1 rowspan=1 > Opponent </th><th colspan=1 rowspan=1 > Result </th><th colspan=1 rowspan=1 > Location </th><th colspan=1 rowspan=1 > Notes </th></tr>
<tr> <th colspan=7 rowspan=1 > No. 27 Squadron RFC </th></tr>
<tr> <td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > 1 May 1917 </td><td colspan=1 rowspan=1 > Martinsyde G.100 </td><td colspan=1 rowspan=1 > Albatros D.III </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 > Near Épinoy </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=2 > 4 June 1917 1415 </td><td colspan=1 rowspan=2 > Martinsyde G.100 (A6262) </td><td colspan=1 rowspan=1 > Albatros D.III </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > West of Sint-Denijs-Westrem </td><td colspan=1 rowspan=1 > Shared with Lieutenant D. V. D. Marshall </td></tr>
<tr> <td colspan=1 rowspan=1 > 3 </td><td colspan=1 rowspan=1 > Albatros D.III </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 > Hausbeke </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <th colspan=7 rowspan=1 > No. 78 Squadron RFC </th></tr>
<tr> <td colspan=1 rowspan=1 > u/c </td><td colspan=1 rowspan=1 > 25 September 1917 </td><td colspan=1 rowspan=1 > Sopwith 1½ Strutter </td><td colspan=1 rowspan=1 > Gotha G.V </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > South of Brentwood, Essex – North Sea </td><td colspan=1 rowspan=1 > Shared with observer/gunner Lieutenant G. G. Williams </td></tr>
<tr> <th colspan=7 rowspan=1 > No. 3 Squadron RFC </th></tr>
<tr> <td colspan=1 rowspan=1 > 4 </td><td colspan=1 rowspan=1 > 11 March 1918 1730 </td><td colspan=1 rowspan=1 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 > Quéant–Pronville </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 5 </td><td colspan=1 rowspan=1 > 13 March 1918 1545 </td><td colspan=1 rowspan=1 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Destroyed in flames </td><td colspan=1 rowspan=1 > Villers </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 6 </td><td colspan=1 rowspan=2 > 16 March 1918 0915–0930 </td><td colspan=1 rowspan=2 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=2 > Cambrai </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 7 </td><td colspan=1 rowspan=1 > Type C </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 8 </td><td colspan=1 rowspan=1 > 17 March 1918 1330 </td><td colspan=1 rowspan=1 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Destroyed in flames </td><td colspan=1 rowspan=1 > Cagnicourt </td><td colspan=1 rowspan=1 > Shared with 2nd Lieutenant A. A. M. Arnot </td></tr>
<tr> <td colspan=1 rowspan=1 > 9 </td><td colspan=1 rowspan=1 > 22 March 1918 1430 </td><td colspan=1 rowspan=1 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Destroyed in flames </td><td colspan=1 rowspan=1 > Havrincourt Wood </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 10 </td><td colspan=1 rowspan=3 > 23 March 1918 1540–1545 </td><td colspan=1 rowspan=3 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > Balloon </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=3 > Quéant </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 11 </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 12 </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 13 </td><td class="highlighted"  colspan=1 rowspan=1 > 27 March 1918 abt 0700 </td><td class="highlighted"  colspan=1 rowspan=1 > Sopwith Camel (C1615) </td><td colspan=1 rowspan=1 > LVG C </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > Fricourt </td><td colspan=1 rowspan=1 > Shared with Lieutenants George Riley and W. C. Dennett </td></tr>
<tr> <th colspan=7 rowspan=1 > No. 3 Squadron RAF </th></tr>
<tr> <td colspan=1 rowspan=1 > 14 </td><td class="highlighted"  colspan=1 rowspan=1 > 1 April 1918 1815 </td><td class="highlighted"  colspan=1 rowspan=1 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Fokker Dr.I </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > Combles </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 15 </td><td colspan=1 rowspan=1 > 8 April 1918 0655 </td><td colspan=1 rowspan=1 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Balloon </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > North of Mory </td><td colspan=1 rowspan=1 > Shared with Captain Cyril Ridley </td></tr>
<tr> <td colspan=1 rowspan=1 > 16 </td><td colspan=1 rowspan=1 > 11 April 1918 1600 </td><td colspan=1 rowspan=1 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Albatros C </td><td colspan=1 rowspan=1 > Destroyed in flames </td><td colspan=1 rowspan=1 > Ervillers </td><td colspan=1 rowspan=1 > Shared with Lieutenants Lloyd Hamilton, Adrian Franklyn, and C. E. Mayer </td></tr>
<tr> <td colspan=1 rowspan=1 > 17 </td><td colspan=1 rowspan=2 > 12 April 1918 1900–1915 </td><td colspan=1 rowspan=2 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > Albert </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 18 </td><td colspan=1 rowspan=1 > Albatros D.V </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 > Pozières </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 19 </td><td colspan=1 rowspan=1 > 20 April 1918 1750 </td><td colspan=1 rowspan=1 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Fokker Dr.I </td><td colspan=1 rowspan=1 > Destroyed </td><td colspan=1 rowspan=1 > North-East of Villers-Bretonneux </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 20 </td><td colspan=1 rowspan=1 > 27 May 1918 1240 </td><td colspan=1 rowspan=1 > Sopwith Camel (C6730) </td><td colspan=1 rowspan=1 > Type C </td><td colspan=1 rowspan=1 > Out of control </td><td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > Shared with Lieutenants Lloyd Hamilton and Will Hubbard </td></tr>
</table>
Question:
On April 1st 1918 which Camel version did Douglas John Bell switch to from C1615?
Answer:
In April, Douglas John Bell had switched to Camel C6730 from C1615 (March).