A person climbs up a stalled escalator in 60 s .If standing on the same but escalator running with constant velocity he takes 40 s.How much time is taken by the person to walk up the moving escalator ?

Question

$(a)\;37\;s \qquad(b)\;27\;s\qquad(c)\;24\;s\qquad(d)\;45\;s$