$18.$ A coal$-$fired power plant would like to increase its efficiency. One potential suggestion is to reduce the air preheater flue gas outlet temperature to $250\backslash$deg F$,$ to extract additional heat from the flue gas before it discharges into the stack. This plant burns high sulfur coal and the SO$2$ concentration in the flue gas has been measured at $1,200$ ppm$.$ The moisture content of the flue gas is $10\%.$ Estimate the modified flue gas sulfuric acid dew point temperature and provide comments to the plant on the repercussions of this suggestion, as well as recommendations to alleviate side problems resulting from the implementation of the suggested operational change.