A man ${\mathrm{M}}_1 \mathrm{of} \mathrm{mass} 80 \mathrm{kg} \mathrm{runs} \mathrm{up} \mathrm{a} \mathrm{staricase} \mathrm{in} 15 \mathrm{s}. \mathrm{Another} \mathrm{man} {\mathrm{M}}_2$ also of mass 80 kg runs up the same staircase in 20 s. The ratio of the power developed by them will be: