We have purchased flats from the builder in an Apartment in A.P., The builder have sold entire flats (20 nos.) in the Apartment and registered 90% of the land to the flat buyers (20 flats). The remaining 10% (720 sft) is kept with him with an intention to construct penthouse and sale. Actually the plan was approved for 20 flats only. Whether he has right to do this. If he is not right, in what way we have to proceed further legally. Please guide.