SOLVED: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 tonnes (metric tons) per second. (a) Give upper and lower estimates for the total quantity Q(6) of erupted materials alter six seconds. (b) Use the Midpoint Rule to estimate Q(6) .