optimizing using fminimax the error

Hello,

I am now working on optimizing a heating tank control system. My objective function to be minimaxed is I = integral ( (T-Ts)^2 ). I have introduced my differential equation dT/dt and have calculated several T values at specific time intervals using given values of Q, Tf, V, rho, Cp, F. However, now I would like to use fminimax to find the minmax of my objective function and I want it to change the values of Q and Tf to find the optimal solution. I am not sure how to do so since Q and Tf are also needed in my differential equations to calculate the T values. I have attached my work below, please have a look and help me out!

Vanessa