Income tax on Sale of House Property

Hi all,

Scenario  : 

Suppose Mr.A possess 10 cents of land and house property . 

Purchase date : 01/01/1991 @ consolidated cost of Rs.10 lakhs

Sales date 01/01/2020 @ consolidated cost of Rs.100 lakhs.

On what amount Income Tax will be assessed? 

Sub scenario - what will be his Income tax liability..

a)If he buys another property of 100 lakhs before March 31st ?

b)If he could not buy another property of the same value as on 31st March.

Please have your views.

regards,

Saqif