What is the fine-grained topic of the following text: In the first stage of the investment, building D will be built, where you will find 24 flats, 2 and 3 rooms, with area from 42.4 to 56.9 m2, and building A and B, where 54 single, double and three-room flats will be built from 35 to 52 m2. Only return the topic.
Investment stages in constructing residential buildings