The base of an isosceles triangle is $12 cm$ and its perimeter is $32 cm$. Its area is $x c{m}^2$.Find the value of $x$?

In the given figure, ABCD is a rectangle in which AB$=60 cm$ and BC$=40 cm$. If P, Q, R and S be the mid-points of AD, DC, CB and BA, the area of the shaded region is $x c{m}^2$. Find the value of $x$?