What would be the mean temperature on the Earth’s surface if we ignore the greenhouse effect, assume that the Earth is a perfect black body whose orbit around the Sun is circular and take into account its non-vanishing albedo?

Given that,

Average Earth-Sun distance = 149.6 million km

Radius of the Sun = 695,510 km

Effective temperature of the Sun = 5800k

The albedo, $a$ = $0.39$. Your answer should be in SI unit.

To know more about the temperature range for the Habitable zone.

Astrophysics Thermodynamics