Which of the following phrases defines the nature of the 'Hundi' generally referred to in the sources of the post-Harsha period?

In India, instruments of credit have been in use since time immemorial and are popularly known as Hundies. The movement of goods during Medieval period was facilitated by the growth of a financial system which permitted easy transfer ofmoney from one part of the country to another. This was done through the use of Hundis. The Hundis was a letter of credit payable after a period of time at a discount.