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Hello i need some with trigonometric substitutions. [tex]\int\limits^a_b {x} \, dx[/tex]

Isee the amount was $90.00 then reduced to $75.00 , what is the percent ?

Awater holding tank measures 105 m long, 50 m wide, and 8 m deep. traces of mercury have been found in the tank, with a concen- tration of 60 mg/l. what is the total mass of mercury in the tank? answer in units of kg.