From the circular disc of radius `4R` two small discs of radius R are cut off. The centre of mass of the new structure will be at

A circular disc of radius R is removed from a bigger circular disc of radius 2R such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance aR from the centre of the bigger disc. The value of a is

A circular disc of radius R is removed from a bigger circular disc of radius 2R such that the cirucmferences of the discs coincide. The centre of mass of the new disc is alpha/R from the center of the bigger disc. The value of alpha is

A circular disc of radius R is removed from a bigger circular disc of radius 2R such that the cirucmferences of the discs coincide. The centre of mass of the new disc is alpha/R from the center of the bigger disc. The value of alpha is