A power station consists of three synchronous generators of rating 500 MVA, 750 MVA, and 1000 MVA with inertia 0.8 pu, 0.6, and 0.5 pu respectively on their own buses MVA rating. The equivalent pu inertia constant on 200 MVA common base is:
1
4.75 pu
2
6.25 pu
3
4.25 pu
4
6.75 pu