Find centre of mass of a lamina.

[Calu]

A lamina comprises a uniform rectangular card ABCD where AB = 10 cm and BC = 12 cm
with a circle of radius 3 cm cut out. The centre of the circle is 7 cm from AB and 4 cm from AD.

How would I find the centre of mass for this lamina? I know to find the centre of mass for a uniform lamina we can integrate or simple find the centre of the shape's diagonals. Also, how would I find it if the circle was added on top instead? I'm sorry I don't have much of an idea how to do these.

 

[SteamKing]

You can use the principle of moments to calculate the c.o.m. of the lamina.