Look at the drawing given in the figure which has been drawn with ink of uniform line-thickness. The mass of ink used to draw each of the two inner circles, and each of the two line segments is `m`. The mass of the ink used to draw the outer circle is `6m`.
The coordinates of the centres of the different parts are: outer circle `(0, 0)`, left inner circle `(-a, a)`, right inner circle `(a, a)`, vertical line `(0, 0)` and horizontal line `(0, -a)`. The `y`-coordinate of the centre of mass of the ink in this drawing is