The luminosity of our Sun could be derived by the Stefan-Boltzmann, otherwise known as Luminosity law. It says the total energy produced by a unit surface per unit time area (power per unit area) is: (power per unit area)=(Stefan-Boltzmann constant)(Temperature)4 That means the luminosity of the Sun is L=(Surface area of the Sun)(Stefan-Boltzmann constant)*(Temperature)4. We are only changing the temperature by a factor 3. That means the luminosity will increase by a factor of 34, since the temperature is present in the formula above with its fourth power. Therefore, the luminosity would increase 81 times.