Xiao Ming participated in four Chinese tests, with an average score of 68. He wants to raise the average score of five times to more than 70 points after the next Chinese test. Then, in the next test, how many points should he score at least.
小明参加了四次语文测验，平均成绩是68分．他想在下一次语文测验后，将五次的平均成绩提高到70分以上，那么，在下次测验中，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>