A method for determining the quantity of dissolved oxygen in natural waters requires a series of redox reactions. Balance the following chemical equations in that series under the conditions indicated:
(a) In basic solution: Mn2+(aq)+O2(g) -----> MnO2(s)
(b) In acidic solution: MnO2(s)+I-(aq) ------> Mn2+(aq)+I2(s)
(c) In neutral solution: I2(s)+S2O3 2-(aq) ------> I-(aq)+S4O6 2-(aq)