Temporary hardness of a sample of ground water is due to presence of compound P and Q. Boiling the sample of water converts compounds P and Q to compounds R and S respectively. Compound S imparts red colouration to flame on performing flame test. Correct combination(s) among the following is (are)I.  P: Mg(HCO3)2; R: MgCO3II. Q: Ca(HCO3)2; S: CaCO3III. P: Mg(HCO3)2; R: Mg(OH)2IV. Q: Ca(HCO3)2; S: Ca(OH)2