In order to save water, a city has the following regulations on water use for users: large households (those with a family population of 4 or more) use less than 15 cubic meters of water per month, and small households (those with a household population of 3 or less) use 10 cubic meters of water per month. The water fee of 0.8 yuan per cubic meter is charged for the water consumption within the cubic meter; the water fee for the excess part is doubled per cubic meter for the water consumption exceeding the above. If a user has 5 members and actually uses 25 cubic meters of water this month, how much should this household pay for water this month?
为节约用水，某市对用户用水规定如下：大户(家庭人口4人及4人以上者)每月用水15立方米以内的，小户(家庭人口3人及3人以下者)每月用水10立方米以内的，按每立方米收取0.8元的水费；超过上述用水量的，超过部分每立方米水费加倍收费．某用户5口人，本月实际用水25立方米，则这户人家本月应缴纳水费多少元？
<gadget id="calculator">15 * 0.8</gadget>
<output>12</output>

<gadget id="calculator">25 - 15</gadget>
<output>10</output>

<gadget id="calculator">10 * 0.8 * 2</gadget>
<output>16</output>

<gadget id="calculator">12 + 16</gadget>
<output>28</output>

<result>28</result>