m = 299кг
N = 4
S = 50см^2
p - ?
p = F/S F = mg
p = mg/4S
p = 299*9,8/4*0,005 =146510Па
кпд=А/N A=n*m*g*h кпд= n*m*g*h/N=2*430*10*0,4/8,82*10^3=0,39=39%