Tax on money given by mother after selling of house

If she sells the house, she will be liable to capital gain. In order to avoid that, she may gift the house in favor of her 3 sons, and then the 3 sons may sell the house, and invest in some other property to save tax.

How much capital gain tax she has to pay (say if selling amount is 25 lac)

What if she purchase a property on the name of all 3 sons with same amount?

Actually if she sells it will be easy to sell... but if she gift to 3 sons...then it will tedious to sell by all 3 (as they are not in same country).

One has to compute the long term capital gain.

Sale Consideration = Rs. XXX

Less Indexed cost of acquisition = Rs. XXX

Equal Long term capital gain = Rs. XXX (this amount is to be invested to avoid tax. She cannot gift this amount to her 3 sons to avoid tax.)

Hi,
purchase cost of land was 20,000 rs. in 1993. My father constructed a house on that land where construction completed in 1998. There is no proof of house construction cost which was I think round about 7-8 lac.

Now selling price is about 25 lac.

So how much tax she has to pay on this transaction?

Is this taxable amount only she has to invest to avoid tax?

Regards, 
Kunal