The graph shows the percentage of households in a certain city watching television during a 24-hr period on a weekday (t=0 corresponds to 6 a.m.). By computing the slope of the respective tangent line, estimate the rate of change of the percentage of households watching television at a-8 p.m. Note that dy = 2.1 y (%) 30 38 22.5 15 7.5 2 4 6 8 10 12 14 16 18 20 22 (00)