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:
M35 series 2½-ton 6x6 cargo truck
Table title:
Weight
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Model </th><th colspan=1 rowspan=1 > Type </th><th colspan=1 rowspan=1 > wheelbase </th><th colspan=1 rowspan=1 > Empty Weight </th><th colspan=1 rowspan=1 > Loaded Weight </th></tr>
<tr> <td colspan=1 rowspan=1 > M44 </td><td colspan=1 rowspan=1 > Chassis (single rear tires) </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 10,225 lb (4,638 kg) </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > M45 </td><td colspan=1 rowspan=1 > Chassis </td><td colspan=1 rowspan=1 > short </td><td colspan=1 rowspan=1 > 10,524 lb (4,774 kg) </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > M46 </td><td colspan=1 rowspan=1 > Chassis </td><td colspan=1 rowspan=1 > extra long </td><td colspan=1 rowspan=1 > 10,860 lb (4,930 kg) </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > M57 </td><td colspan=1 rowspan=1 > Chassis (single rear tires) </td><td colspan=1 rowspan=1 > short </td><td colspan=1 rowspan=1 > 10,943 lb (4,964 kg) </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > M58 </td><td colspan=1 rowspan=1 > Chassis </td><td colspan=1 rowspan=1 > short </td><td colspan=1 rowspan=1 > 10,441 lb (4,736 kg) </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > M34 </td><td colspan=1 rowspan=1 > Cargo (single rear tires) </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 11,775 lb (5,341 kg) </td><td colspan=1 rowspan=1 > 17,125 lb (7,768 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M35 </td><td colspan=1 rowspan=1 > Cargo </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 12,465 lb (5,654 kg) </td><td colspan=1 rowspan=1 > 17,815 lb (8,081 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M36 </td><td colspan=1 rowspan=1 > Cargo (long bed) </td><td colspan=1 rowspan=1 > extra long </td><td colspan=1 rowspan=1 > 14,280 lb (6,480 kg) </td><td colspan=1 rowspan=1 > 19,580 lb (8,880 kg) </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > M48 </td><td class="highlighted"  colspan=1 rowspan=1 > Tractor </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 11,430 lb (5,180 kg) </td><td colspan=1 rowspan=1 > 18,780 lb (8,520 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M49 </td><td colspan=1 rowspan=1 > Gasoline, tank </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 13,895 lb (6,303 kg) </td><td colspan=1 rowspan=1 > 19,245 lb (8,729 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M50 </td><td colspan=1 rowspan=1 > Water, tank </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 15,184 lb (6,887 kg) </td><td colspan=1 rowspan=1 > 20,534 lb (9,314 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M59 </td><td colspan=1 rowspan=1 > Dump </td><td colspan=1 rowspan=1 > short </td><td colspan=1 rowspan=1 > 14,050 lb (6,370 kg) </td><td colspan=1 rowspan=1 > 19,400 lb (8,800 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M60 </td><td colspan=1 rowspan=1 > Light wrecker </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 23,960 lb (10,870 kg) </td><td colspan=1 rowspan=1 > 27,810 lb (12,610 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M108 </td><td colspan=1 rowspan=1 > Crane </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 19,375 lb (8,788 kg) </td><td colspan=1 rowspan=1 > 23,225 lb (10,535 kg) </td></tr>
<tr> <td colspan=1 rowspan=1 > M109 </td><td colspan=1 rowspan=1 > Shop Van </td><td colspan=1 rowspan=1 > long </td><td colspan=1 rowspan=1 > 15,231 lb (6,909 kg) </td><td colspan=1 rowspan=1 > 20,581 lb (9,335 kg) </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > M275 </td><td class="highlighted"  colspan=1 rowspan=1 > Tractor </td><td colspan=1 rowspan=1 > short </td><td colspan=1 rowspan=1 > 11,179 lb (5,071 kg) </td><td colspan=1 rowspan=1 > 18,529 lb (8,405 kg) </td></tr>
</table>
Question:
How many Tractor variants were developed and what were their models?
Answer:
Two tractor variants were developed, the M48 and M275.