An advertising agency has found that when it promotes a new product in a city the weekly rate of change R of the number of people who are aware of the promotion follows a linear pattern. The weekly rate of change R of people who are aware of the promotion x weeks after it is introduced is described by the equation R = 1800-60x. Find the x- and R-intercepts and then graph the function on a viewing window that is meaningful in this application. What is the x-intercept? (Type an integer or a fraction.)