Exchange

Miriam bought a gold chain from Muscat, like she always does, just before her trip to India.
Once in India, she thought she should get a different pattern. Not difficult, because in her hometown in India, there was showrroom of the same same jeweller from whom she had bought the gold chain.
The chain was only 4 days old in her possession, and it was worn only during the flight. The branch agreed to exchange, but, she would have to pay making charges once again.
"well this is 40 grams, if I dont pay any money, but want just another chain, what could be the weight of my new chain? Mirium wanted to know.
And the reply was
"30 gms Madam"