A parallelogram has a base of 12 decimeters and a height of 4 decimeters. If the height increases by 1 decimeter, how much does its area increase?
一个平行四边形，底是12分米，高是4分米，如果高增加1分米，它的面积增加多少平方分米．
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">12 * 5</gadget>
<output>60</output>

<gadget id="calculator">12 * 4</gadget>
<output>48</output>

<gadget id="calculator">60 - 48</gadget>
<output>12</output>

<result>12</result>