1. The local Environmental Control agency for the Antamina Project charges $60,000 a month for river water monitoring. It had been their practice to send out bills to their 24 customers at the end of each month period. Thus, at the end of February it would send a bill to each customer of $120,000 for water monitoring during January and February.

Recently the firm changed its billing date: it now sends out the 2-month bills after one months service has been performed. Bills for January-February, for example, are sent out at the end of January. External auditors claim that the Agency is receiving half its money before the water monitoring. This unearned money, the auditors say, could be temporarily invested for one month at 1% per month interest by the EC Agency.

Compute how much extra income the EC Agency could earn each year if it invests the money as described by the auditors.