Georgia filled her kitchen sink up with water so that she could do the dishes. When she was done with the dishes, she pulled out the drain stopper so the water could begin to drain out of the sink. A linear model of this situation contains the values (2 , 7.4) and (4 , 6.8), where x represents the number of seconds, and y represents the water level in the sink, in inches.
What is the rate of change in this linear model?