
Answer:
Ending Balance Due = $14,980.106
Total Interest = $780.106
Explanation:
solution
Total Interest and Ending balance due by the U.S. Rule are as given below
so interest is here for 70 day with 12 % of 21000
interest = 0.12 × 21000 ×  [tex]\frac{70}{360}[/tex]
interest = $490
so
payment = $2400 - $490
payment = $1,910
and adjusted balance  will be after that
adjusted balance  = $21,000 - $1,910
adjusted balance  = $19,090
and
on 100 day
Interest  =  0.12 × $19,090  ×  [tex]\frac{30}{360}[/tex]
Interest  =  $190.9
and
Payment  = $4,400 - $190.9
payment = $4209.1
So
adjusted balance  = $19090  - $4209.1
adjusted balance  = $14,880.9
and interest = $14,880.9 × 0.12  ×  [tex]\frac{20}{360}[/tex]
interest = $99.206
so Ending Balance Due  will be
Ending Balance Due = $14,880.9 + $99.206
Ending Balance Due = $14,980.106
and
Total Interest = $490 + $190.9 + $99.206
Total Interest = $780.106