There are currently six iron chains, and there are four closed iron rings on each section. Now we need to open some iron rings and weld these 24 iron rings into a circle. If it takes two minutes to open a hoop. It takes three minutes to weld a hoop. So how many minutes will it take to weld this circle at least?
现有六条铁链，每段上有四个封闭的铁环，现在要打开一些铁环，把这24个铁环焊接成一个圆圈．如果打开一个铁环要两分钟．焊接上一个铁环要三分钟．那么焊接成这个圆圈至少要多少分钟．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

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

<result>25</result>