On a hike, Oscar's elevation change after 12 minutes was -84 feet. Assuming his elevation was changing at a constant rate, what integer represents his elevation change per minute. Please show work.

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. what distance from city a is the point where the truck and the car will meet?