A uniform L-shaped metal plate is formed by welding together two identical square plates, each 0.20 m on a side. One square is positioned with its edges along the positive x- and y-axes and its lower-left corner at the origin. The second square is attached directly above the first so that they share the entire top edge of the first square. Determine the y-coordinate of the center of mass of the composite plate.
a) 0.15m
b) 0.20m
c) 0.25m
d) 0.23m