Error 55 Endogenous operands for /

[Setha25]

Does anyone know why these constraints are giving me error 55? I cannot figure out how they are non linear. I have to use an LP to solve the problem.
c9..
P1 =e= 36/R1;
c10..
P2 =e= 36/R2;
c11..
P3 =e= 36/R3;
c12..
P4 =e= 16/R4;


entire code:

free variable power;
NonNegative Variables R1,R2,R3,R4,P1,P2,P3,P4;
equations obj, c1,c2,c3,c4,c5,c6,c7,c8,c9,c10,c11,c12;

obj..
power =e= P1 + P2 + P3 + P4;

c1..
R1 =g= 1;
c2..
R1 =l= 3;

c3..
R2 =g= 1;
c4..
R2 =l= 3;

c5..
R3 =g= 1;
c6..
R3 =l= 3;

c7..
R4 =g= 2/3;
c8..
R4 =l= 2;


c9..
P1 =e= 36/R1;
c10..
P2 =e= 36/R2;
c11..
P3 =e= 36/R3;
c12..
P4 =e= 16/R4;


model number3 /all/;
solve number3 using lp minimizing power;

[Fred]

Hi,

in equations c9,c10,c11,c12 you divide by a variable which means that the model is non-linear.

I hope this helps!

Fred