c
(c) Suppose \(d = \) distance of epicenter of Earth quake from point of observation 

\(v_S\) = Speed of \(S-wave\) and \(v_P\) = Speed of P-wave then \(d = {v_P}{t_P} = {v_S}{t_S}\) or \(8\,{t_P} = 4.5\,{t_S}\) 

==> \({t_P} = \frac{{45}}{8}{t_S},\) given that \({t_S} - {t_P} = 240\) ==> \({t_S} - \frac{{4.5}}{8}{t_S} = 240\) 

==> \({t_S} = \frac{{240 \times 8}}{{3.5}} = 548.5\,s\)  

\(\therefore\) \(d = {v_S}{t_S} = 4.5 \times 548.5\)\( = 2468.6 \approx 2500\,km\)