Answer:
$ 454.86 : $33.25
Step-by-step explanation:
1.
Alex bought the new easy chair for $ 399 .
If she pays the amount in 13th month. So, she has to pay the interest of 1 month too , which is, = $ 
= $ 55.86
So, total amount she has to pay for the chair,
= (cost price of the chair + interest)
= $ (399 + 55.86)
= $ 454.86 (answer)
2.
If she wants to pay the amount within the 12 months, so that she doesn't have to pay the interest, her budget for that for each month will be ,
$ 
= $ 33. 25 (answer)
Answer: Third option.
Please, see the detailed solution in the attache file.
Thanks
Penny- 3g
nickel-5g
dime- 2g
quarter-6g
half dollar- 11g