Answer: authority built flats in 2010 = 63,85,196
authority built flats in 2011 = 23,48,967
Step-by-step explanation: total flats in 2 years = flats built in 2010 + flats built in 2011
total flats built in two years = 63,85,196+23,48,967
total flats built in two years = 87,34,163