A water has a pH = 7.4 and an alkalinity of 400 mg/l as CaCO3. The first dissociation constant for carbonic acid (H2CO3) is K1 = 4.45e-7. Assume all activity coefficients are equal to 1.0. What is the concentration of carbonic acid in moles/liter?, mg/l as H2CO3?, mg/l as CaCO3?