A power plant generates electricity by burning oil. Pollutants produced as a result of the burning process are removed by scrubbers in the smokestacks. Over time, the scrubbers become less efficient and eventually they must be replaced when the amount of pollution released exceeds government standards. Measurements are taken at the end of each month determining the rate at which pollutants are released into the atmosphere, recorded as follows. Complete parts (a) and (b). Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pollutant release rate 0.18 0.25 0.28 0.34 0.37 0.46 0.64 0.68 0.81 0.87 0.89 0.97 (tons/day) a. Assuming a 30-day month and that new scrubbers allow only 0.05 ton/day to be released, give an upper estimate of the total tonnage of pollutants released by the end of June. What is a lower estimate? First, what should be the length of each subinterval? (Type an integer or a decimal.)