A ball dropped from the top of the building can be modeled by the function f(t)=-16t^2 + 36 , where t represents time in seconds after the ball was dropped. A bee's flight can be modeled by the function, g(t)=3t+4, where t represents time in seconds after the bee starts the flight.
Since its telling you that x is the number of years and the question is "How much does the cost of milk increase EVERY YEAR" then you can conclude that the cost is increasing by 0.25 each year