Suppose that a volcano is erupting and readings of the rate r(t) at which solid materials are spewed into the atmosphere are given in the table. The time t is measured in seconds and the units for r(t) are measured in tonnes (metric tons) per second. Note that r(t) is increasing over the interval [0, 6]. t 0 1 2 3 4 5 6 r(t) 28 18 34 48 54 60 (a) Give upper and lower estimates (in tons) for the total quantity Q(6) of erupted materials after six seconds. (Use six equal subintervals.) lower estimate Q(6) tons upper estimate tons = 016) (b) Use the midpoint rule to estimate Q(6) (in tons). (Use three equal subintervals.) Q(6) = tons Oil leaked from a tank at a rate of r(t) liters per hour. The rate decreased as time passed, and values of the rate at two-hour time intervals are shown in the table. t(h) 0 2 4 6 8 10 r(t) (L/h) 8.6 7.5 6.7 6.4 5.7 5.1 Find lower and upper estimates for the total amount of oil in liters) that leaked from the tank over the interval [0, 10]. (Use five equal subintervals.) lower estimate upper estimate