$($f$)(2$ points$)$ A well$-$insulated rigid tank having no external work interaction is divided into two equal volumes by an internal partition. Each side contains an equal mass of gas with the same temperature, but at different pressures. The partition is removed and the gases mix until equilibrium is reached. Which of the following statements is true?

Total internal energy of the two gases increases

Total internal energy of the two gases decreases

Total entropy of the two gases increases

Total entropy of the two gases decreases

System operates as a cycle and all the properties remain unchanged