In the table, x represents minutes, and y represents the altitude of an airplane.

Altitude of an Airplane
Minutes, x
Altitude in feet, y
15
22,500
20
20,000
25
17,500
30
15,000

Which statement is correct about the slope of the linear function that the table represents?
The slope is positive because as the minutes decrease, the altitude increases.
The slope is positive because as the minutes increase, the altitude increases.
The slope is negative because as the minutes decrease, the altitude decreases.
The slope is negative because as the minutes increase, the altitude decreases.