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 = $5800$K

Answer using three significant digits.

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

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

Source: IOAA 2013