The average score of Wan Ming's last 4 math tests is 68, and he wants to raise the average score to over 70 after the next math test. So what is the minimum score he needs for the next math test?
万明最近4次数学测验的平均分是68分，他想在下次数学测验后将平均分提高到70分以上．那么下次数学测试他至少要得多少分？
<gadget id="calculator">70 * 5</gadget>
<output>350</output>

<gadget id="calculator">68 * 4</gadget>
<output>272</output>

<gadget id="calculator">350 - 272</gadget>
<output>78</output>

<result>78</result>