4 [11 pts] Let y = f(x) be the function graphed below on the interval [0, 9]. y = /(z) -5 The areas of the four regions determined by the r-intercepts (1, 0), (5,0), and (8, 0) lie either above or below the x-axis and are labeled as in the figure. Their values are A1 = As = 5, A2 = 10, and A4 = 4. a) Express the integral fo f (x) da in terms of A1, A2, As, and As. Calculate its value. b) Express the integral fo f(x) da in terms of A1, A2, As, and A4. Calculate its value. c) Express the area of the region encloded by the graph of f and the r-axis in terms of A1; A2, As, and A4. Calculate its value. d) If the units of f(x) are dollars / item and r is the number of items, then what are the units of fo f(x)de