I am trying to solve a system that has 5 unkown variables. I have 4 equation and a if statment in order to solve the system as it can be seen in the figure.
The problem is that nch4(t) and nar(t) are the input variables. If i put the IF EXPRESSION before the equation i get this error: "Error, cannot determine if this expression is true or false: 2 <= nar(t)/nch4(t)", because those variables are not defined.
Any idea on how can i get this right?