T = 
        2.25*k1/P^2 + 2.25*k2/Q^2;
Vne = -2*3*Z/(2*P) - 
          2/(r + R) - (3 - (r/Q)^2)/Q - 
          Z*(3 - (R/Q)^2)/Q;
Vee = 
        2*(3 - (R/Q)^2 - 0.6*(P/Q)^2)/Q + 3*s1/P + 
          3*s2/Q;
Vnn = Z/(r + R);
func = T + Vne + Vee + Vnn;
  
c = {k1 ->  1.02480344,  k2 ->  1.232443643, 
          s1 ->  0.27877144, s2 ->  0.28887416,  
          Z  ->  3.0};
func  =  func  /.  c
N[t = FindMinimum[func,  {P, 0.5}, {Q, 1.2  }, {R, 0.5}, {r, 0.6}], 
      10]
u  =  t[[2]];
  
N[Vne  /.  u  /.  c,  10]
  
N[Vee  /.  u  /. c,  10]
  
N[Vnn  /.  u  /. c, 10]
  
N[-(Vne + Vee + Vnn)/T  /.  u  /.  c,  10]