In a cuboid anhydrous ornamental fish tank with length, width and height of 46cm, 25cm and 28cm respectively, there is a rockery with a height of 18cm and a volume of 4200cm**3. If the water pipe injects water into the fish tank at a flow rate of 8dm**3 per minute. So at least how long will it take to completely submerge the rockery?
在一个长、宽、高分别为46cm、25cm、28cm的长方体无水观赏鱼缸中，放有一块高为18cm、体积为4200cm**3的假山石．如果水管以每分8dm**3的流量向鱼缸内注水．那么至少需要多长时间才能将假山石完全淹没？
<gadget id="calculator">46 * 25 * 18</gadget>
<output>20_700</output>

<gadget id="calculator">20_700 - 4_200</gadget>
<output>16_500</output>

<gadget id="calculator">16_500 / 1_000 / 8</gadget>
<output>33/16 = around 2.0625</output>

<result>33/16 = around 2.0625</result>