Capital gain

Dear Experts,

One of my relative has sold inheritated agriculture land in april 2018 for Rs.2700000. The land is in rural area. Now my query is,

1.Does it attract a capital gain?  if yes then how could we calculate a capital gain if purchase amount is not known.

2.What if, if it in urban area?

3.Do we need to show such amount while filling income tax return?

Thanks in advance.