No 7 bantuin ya + caranya

F = [tex] \frac{W}{F} = \frac{lf}{lw} [/tex]
F = lw. W / lf
   = 0,4 m x 50 kg / 1,6 m
   = 12,5 N
KM = W/F = 50/12,5 = 4 kali

Kuasanya coba dicek lagi y, maaf :'(