You need 200 mL of a 10% alcohol solution. On hand, you have a 25% alcohol mixture. How much of the 25% alcohol mixture and pure water will you need to obtain the desired solution? I need help

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.