f(x)=(2/3)x^1.5
The centroid position along the x-axis can be obtained by
integrating the function * x to get the moment about the y-axis,
then divide by the area of the graph,
all between x=0 to x=3.5m.
Expressed mathematically,
x_bar=(∫f(x)*x dx )/(∫ f(x) dx limits are between x=0 and x=3.5m
=15.278 m^3 / 6.1113 m^2
=2.500 m