How to calculate income from multiple House Properties?

I am salaried employee with salary of Rs100000 p.m.(Out of which 12000 is H.R.A.). I have 3 houses for which I’ve taken loans from different banks. All houses are vacant. In addition I pay House Rent of Rs 10000 p.m. My question is how much I can claim as loss from House Property against these houses. And can I claim exemption for H.R.A.?