Milton has his money invested in a stock portfolio. The value, v(x), of his portfolio can be modeled with the function v(x)=30,000(0.78)^x, where x is the number of years since he made his investment. Which statement describes the rate of change of the value of his portfolio? (1) It decreases 78% per year. (2) It decreases 22% per year. (3) It increases 78% per year. (4) It increases 22% per year.