The following is given:

20 ml of HCl (2.0 M) added with
5 ml of Na2S2O3 (0.3 M) with
5 ml of H2O

S2O3^-2(aq) + 2H^+1 (aq) --> S (s) + SO2 (g) + H2O (l)

Calculate the following:

a) Reaction rate when 30 mg of sulphur is formed (in 30 ml of solution) after 55 seconds.

b) Rate of reaction in terms of (moles of thiosulphate ion) consumed per litre per second for the reacting solution.