Capital gains taxation query vip 1

Hi,

Can anyone comment on the LTCG taxation on sale of house property in following case?

Year 1 ltcg 50 lakh on sale of house property. Bonds purchased under section 54EC 40 lakhs. Amount deposited in CGAS 20 lakhs. How much will be the ltcg liable to tax - a. 0 lakh, b. 10 lakhs, c. 30 lakhs.

Year 4 no property purchased hence nil withdrawl from Cgas. How much will be the ltcg liable to tax - a. 0 lakh, b. 10 lakh, c. 20 lakh, d. 50 lakh.

Please also give the reasons why?