Final answer:
The total savings in interest by using a 15-year mortgage would be $116,640.
Step-by-step explanation:
To find the total savings in interest by using a 15-year mortgage, we first need to calculate the total amount paid over 15 years and 30 years for each mortgage.
For the 15-year mortgage, the total amount paid over 15 years would be $730/month x 12 months/year x 15 years = $131,400.
For the 30-year mortgage, the total amount paid over 30 years would be $579/month x 12 months/year x 30 years = $248,040.
The total savings in interest by using a 15-year mortgage would be $248,040 - $131,400 = $116,640.