b
\(\frac{{{\rm{weight}}\,{\rm{of a}}\,{\rm{man}}\,{\rm{in}}\,{\rm{stationary}}\,{\rm{lift}}}}{{{\rm{weight \,of \,a \,man \,in \,downward \,moving \,lift }}}} = \frac{{mg}}{{m(g - a)}} = \frac{3}{2}\)
\(\therefore \frac{g}{{g - a}} = \frac{3}{2}\) \(⇒\) \(2g = 3g - 3a\) or \(a = \frac{g}{3}\)