Five uniform circular plates, each of diameter b and mass m are laidout in a pattern shown. Using the origin shown, find the y co-ordinate of the centre of mass of the five plate system.

• A

  $\frac{\mathrm{b}}{5}$

• B

  $\frac{\mathrm{b}}{3}$

• C

  $\frac{4\mathrm{b}}{5}$

• D

  $\frac{2\mathrm{b}}{5}$