Answer:
$103,875.41
Explanation:
To solve this problem, we can use the formula for compound interest:

Given values:
- P = $240,000
- r = 1.2% = 0.012
- n = 6 (bi-monthly)
- t = 30 years
Note: Bi-monthly means every 2 months.
Substitute the given values into the formula and solve for A:




So after 30 years, Mr. and Mrs. Rainer will have paid a total of $343,875.41, which includes both the principal and the interest.
To find the amount of interest they paid, subtract the principal:
Interest paid = $343,875.41 - $240,000 = $103,875.41
Therefore, they will have paid $103,875.41 in interest over the 30-year period.