Select all of the situations that represent a linear relationship between x and y.
the height, y, of a 6-foot tree that grows 0.2 feet per month for x months
the total miles, y, traveled by a car going 62 miles per hour in x hours
the total area, in square meters, y, of a square garden if the side length is x meters
the total cost, y, of a ski rental from a company that charges $15 plus an additional $8 per day rented for x days