Fecal Coliform (FC) concentration in river water was measured as 10780 cfu/100 ml. The FC concentration after the conventional water treatment, but before chlorination, was measured as $23 \mathrm{cfu} / 100 \mathrm{ml}$. The 'Log Kill' (inactivation) of FC due to the conventional water treatment is closest to

A hydrocarbon $\left(\mathrm{C}_n \mathrm{H}_m\right)$ is burnt in air $\left(\mathrm{O}_2+3.78 \mathrm{~N}_2\right)$. The stoichiometric fuel to air mass ratio for this process is

Note: Atomic Weight: $\mathrm{C}(12), \mathrm{H}(1)$

Effective Molecular Weight: Air(28.8)

Ignore any conversion of N 2 in air to the oxides of nitrogen $\left(\mathrm{NO}_{\mathrm{x}}\right)$