A bank pays interest to its customers on the last day of the year. The interest paid to a customer
is calculated as 10% of the average monthly balance maintained by the customer. John is a
customer at the bank. On the last day, when the interest was accumulated into his account, his
bank balance doubled to $5660. What is the average monthly balance maintained by John in his
account during the year? Choose the correct choice from the following answers:
A) 28300	B) 5680	C) 6840	D) 7540	E) 28400
bank balance is doubled with accumulation of interest tp 5660..   this means INTEREST is   5660/2= 
<gadget id="calculator">  5660/2</gadget>
<output>2_830</output>
2830 for entire year..   although since interest is 10% of avg MONthly balance, it becomes 28300..   28300
<result>A</result>
A bank pays interest to its customers on the last day of the year. The interest paid to a customer
is calculated as 10% of the average monthly balance maintained by the customer. John is a
customer at the bank. On the last day, when the interest was accumulated into his account, his
bank balance doubled to $5660. What is the average monthly balance maintained by John in his
account during the year?