Regarding cash deposit

Sir I am an house hold lady and having saving bank account, sir in my account my mother in law has been cash deposited Rs 5.00 lac out of her retirement benefits and my father in law has been deposited Rs 3.00 lac out of maturity of MIS and my husband also deposits Rs 3.00 lack out of the maturity of MIS and whole of the amount tfd in the account of my brother in law for the purpose of purchase of flat at Delhi. Sir now I have received a notice from Income tax deptt to show the source of cash deposit, Sir I requested t to your authority please help me to solve this problem. Thanks