Two engineering teams, A and B, are building roads, and the final workload is allocated with a salary of 8,400 yuan. According to the original planned work efficiency of the two teams, team B should receive a salary of 5,040 yuan. Actually, from the fifth day onwards, the work efficiency of team A has improved 1 times, so that Team A will finally get 960 yuan more salary than the original plan, so how many days did the two teams originally plan to repair the road?
甲、乙两个工程队修路，最终工作量分配8400元工资，两队按原计划的工作效率，乙队应获得5040元的工资，实际从第5天开始，甲队的工作效率提高了1倍，这样甲队最终比原计划多获得960元工资，那么两队原计划多少天能修好这条路？
<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">40 / 7</gadget>
<output>40/7 = around 5.714286</output>

<gadget id="calculator">4 * (40/7)</gadget>
<output>160/7 = around 22.857143</output>

<gadget id="calculator">8 + (160/7)</gadget>
<output>216/7 = around 30.857143</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">3 * (40/7)</gadget>
<output>120/7 = around 17.142857</output>

<gadget id="calculator">12 + (120/7)</gadget>
<output>204/7 = around 29.142857</output>

<gadget id="calculator">(216/7) + (204/7)</gadget>
<output>60</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

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

<result>12</result>