A class of 46 students went rowing. The big boat is limited to 6 people, and the rent for each boat is 20 yuan. The boat is limited to 4 people, and the rent for each boat is 10 yuan. How can I rent a boat? Which option is the most economical? How much is the minimum cost? (seat cannot be empty)
某班46名同学去划船．大船限坐6人，每船租金20元．小船限坐4人，每船租金10元．可以怎样租船？哪种方案最省钱？最少花费多少元？(座位不能为空)
<gadget id="calculator">1 * 20</gadget>
<output>20</output>

<gadget id="calculator">10 * 10</gadget>
<output>100</output>

<gadget id="calculator">20 + 100</gadget>
<output>120</output>

<result>120</result>