can you check this for me?

Question

anonymous · Answer

A certain credit card carries a ten percent simple annual interest rate. If Holly missed her payment one month on an unpaid balance of eight hundred forty dollars, how much interest will she have to pay?

seven dollars

eight dollars and forty cents

seventy dollars

eighty−four dollars

anonymous · Answer

is it 8.40???

anonymous · Answer

i know for a fact that its not the last one

radar · Answer

Usually there is a flat penalty for missed payment, how does this card work, is the penalty equal to the interest for the month of the missed payment?

radar · Answer

If that is the case, it would be $7.00
840 X 10% = $84  now take only one month 1/12 of a year and get $7.00

radar · Answer

I am not sure, how the credit card late payment or missed payment penalty is calculated.