Chemistry in labelling atoms: a small letter after a capital letter belongs to the capital letter, e.g., Pb is a single atom whereas NO3 refers to the molecule consisting of one atom N and three atoms O. For each of the following chemical equations, write down a linear system whose solutions are the amounts of each molecule so that the reaction is balanced. (a) Pb(NO3)2 + NaCl PbCl2 + NaNO3 (b) C2H2Cl4 + Ca(OH)2 C2HCl3 + CaCl2 + H2O