Luminosity for the most massive stars often scales approximately proportional to what power of their mass?

The power of three or even four

The relationship between a star's mass and its luminosity—the total energy it radiates per second—is extremely steep for massive stars. This means that even modest increases in mass result in dramatically amplified energy output. Specifically, the text notes that luminosity for these massive celestial bodies scales incredibly steeply, often being proportional to the mass raised to the power of three or even four ($L \propto M^3$ or $L \propto M^4$). This exponential increase in energy radiated per second is the physical manifestation of the rapid fuel consumption rate, as the star must shine much brighter to support its larger structure against gravity.