A building has 21 floors. One of the floors is the lobby, with a height of 4.2 meters, and the height of each of the other floors is 2.8 meters. How tall is this building?
一幢大楼共有21层．其中一层是大厅，层高4.2米，其余每层的层高都是2.8米．这幢大楼高约多少米？
<gadget id="calculator">21 - 1</gadget>
<output>20</output>

<gadget id="calculator">20 * 2.8</gadget>
<output>56</output>

<gadget id="calculator">4.2 + 56</gadget>
<output>60.2</output>

<result>60.2</result>