Given that the greatest common divisor of A and B is 6, the least common multiple is 84, and A=42, find B.
已知A与B的最大公约数为6，最小公倍数为84，且A=42，求B．
<gadget id="calculator">84 / 42</gadget>
<output>2</output>

<gadget id="calculator">2 * 6</gadget>
<output>12</output>

<result>12</result>