Find the y centroid

Dimensions:

$\backslash$table$[[$a$,$b$,$c$],[42$ mm$,19$ mm$,81$ mm$]]$

Problem Statement:

The curved boundary of the shape shown is a half$-$circle. Given the dimensions above, find:

the $x$ location of the centroid of the shape, and,

the $y$ location of the centroid of the shape

Answers:

$x_{\text{c}\text{e}\text{n}\text{t}\text{r}\text{o}\text{i}\text{d}}=$

y$($centroid $)=$