Xiaohua took part in four simulation exams for math competitions, with an average score of 78. He wants to improve the average score of the five times to at least 80 points after the next mock test, so how many points should he take at least in the next test.
小华参加了四次数学竞赛模拟考试，平均成绩是78分．他想在下一次模拟考后，将五次的平均成绩提高到最少80分，那么下一次考试中，他至少要考多少分．
<gadget id="calculator">80 * 5</gadget>
<output>400</output>

<gadget id="calculator">78 * 4</gadget>
<output>312</output>

<gadget id="calculator">400 - 312</gadget>
<output>88</output>

<result>88</result>