Question 460355
{{{N = k/S}}}, where k is a constant of proportionality.

Now {{{1300 = k/120000}}} ==> {{{k = 1.56 * 10^8}}}

{{{N = (1.56 * 10^8)/S}}}

==> {{{N = (1.56 * 10^8)/(4 * 10^4) = 0.39 * 10^4 = 3900}}}