A certain debt will be paid in 65 installments from January 1 to December 31 of a certain year. Each of the first 20 payments is to be $410; each of the remaining payments is to be $65 more than each of the first 20 payments. What is the average (arithmetic mean) payment that will be made on the debt for the year?  Choose the correct answer
A) 443  B) 455  C) 465  D) 468  E) 475
Total number of installments = 65   Payment per installment for the first 20 installments = 410   Payment per installment for the remaining 45 installments = 410+65= 
<gadget id="calculator">410+65</gadget>
<output>475</output>
475   Average= (20*410 + 45*475)/65= 
<gadget id="calculator">(20*410 + 45*475)/65</gadget>
<output>455</output>
455   Answer 455
<result>B</result>
A certain debt will be paid in 65 installments from January 1 to December 31 of a certain year. Each of the first 20 payments is to be $410; each of the remaining payments is to be $65 more than each of the first 20 payments. What is the average (arithmetic mean) payment that will be made on the debt for the year?