Cpital gain

if you have invested in purchasing the property you will get exemption.  

Yes, you can claim exemption u/s 54 if the gross capital gains arising from sale of both flats is invested in new flat subject to other  conditions being fulfilled.

There have been disputes by department in this regard by narrow interpetation of word "a" appearing in the section with regards to both sold and purchased residential property. However, mostly the matter has been decided in favour of assessee. Recently ITAT decided that the word "a house" should be read as plural in view of General Clauses Act.