$6-6\mathrm{.}21.$ Locate the centroid of the cross section of the culvert shown in Fig. P$-6-6\mathrm{.}21.$

Hint: Integration is unnecessary if the area is subdivided into elements to be found in Table $6-6\mathrm{.}1.$

$\frac{?}{\text{b}\text{a}\text{r}}(y)=3\mathrm{.}46ft$

Ans.