Answer:
[tex]average \ score \ of \ Mari = \frac{72+80+90+73+74+90}{6} = 79.83\\average \ score \ of \ Kai = \frac{56+63+70+100+32+23}{6} = 57.33\\[/tex]
The next test they both score 100
[tex]average \ score \ of Mari = \frac{72+80+90+73+74+90+100}{7} = 82.71\\average \ score \ of Kai = \frac{56+63+70+100+32+23+100}{7} = 63.43\\[/tex]
The increase in average score for Mari is 82.71 - 79.83 =2.88
The increase in average score for Kai is 63.43 - 57.33 = 6.1
Option B. Kai