Answer: $150.
Explanation:
Months remaining = 12 - 4 = 8 months.
Amount remaining to be saved = $1500 - $300 = $1200.
Based off of the given information, we know that Mr. Diaz must save $1200 in the remaining 8 months. In order to find the least amount on average per month that Mr. Diaz must save, we need to divide the $1200 remaining to be saved by the 8 remaining months.
$1200 / 8 months = $150 / month