To find the upper quartile, we first apply the following equation:
[tex]Q=\frac{3}{4}(n+1)[/tex]Where n is the size of the dataset. In this case, there is 10 numbers, then:Q
[tex]Q=\frac{3}{4}(10+1)=\frac{3}{4}(11)=8.25[/tex]Then the upper quartile is the 8th number in the data set. The numbers must be ordered:
[tex]17.4,25.4,26.6,27.1,27.6,28,31.8,35,39.5,40.1[/tex]The 8th number is 35. Hence the answer is C. 35