Ecocity has two potential sources of water supply: groundwater and a small river fed by a mountain spring. The river supports a lot of fish and other wildlife, so the citizens do not want to use any more of it than necessary. Unfortunately, however, their groundwater has barium concentrations in excess of public health standards. Rather than invest money in a treatment plant to reduce the barium concentration of the groundwater to an acceptable level, the citizens decide to blend groundwater with the river water so that the standard is met. Determine the relative amounts of river water and groundwater that should be used, in m^3 per day. DATA: Standard for barium in drinking water = 2mg/L (max allowed), Barium concentration in river water = 0.5mg/L, Barium concentration in groundwater = 9mg/L, Water supply needs for Ecocity = 10 m^3/day