[eqn: {t _{b}} over {t _{t}} = sqrt {{n _{b}} over {n _{t}}}] → [eqn: {t _{b}} over {t _{t}} = sqrt {{`120} over {360}}] → [eqn: t _{t} =1.732t _{b}]

[eqn: {sqrt {{360} over {t _{t}} + {120} over {t _{b}}}} over {240} TIMES 100%=2%]

[eqn: {sqrt {{360} over {1.732t _{b}} + {120} over {t _{b}}}} over {240} TIMES 100%=2%]

[eqn: t _{b} =14.23min]