Xiaolong scored 84 points in each of the 5 tests, and Xiaohai scored 1, 2, 3 and 4 points more than Xiaolong in the first 4 tests, so what is the minimum score Xiaohai should score in the fifth test to ensure 5 tests The average score is at least 3 points higher than Xiaolong.
小龙5次测验每次都得84分，小海前4次测验分别比小龙多出1分、2分、3分、4分，那么小海第五次测验至少应得多少分，才能确保5次测验平均成绩高于小龙至少3分．
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">1 + 2 + 3 + 4</gadget>
<output>10</output>

<gadget id="calculator">15 - 10</gadget>
<output>5</output>

<gadget id="calculator">84 + 5</gadget>
<output>89</output>

<result>89</result>