how could mirza nuruddin possibly know the terms he had demanded of the governor : produce a license for trade within ten days or the two english frigates would weigh anchor and sail ; and accept english sovereigns at bullion value rather than the prevailing discount rate of 4 1/2 percent required to circumvent `` minting time , '' the weeks `` required '' by the shahbandar 's minters to melt down foreign coin and re-mint it as indian rupees .