One of the planets in the Andromeda galaxy, XNP29, has a surface temperature of 120◦K and is hotter than 33% of the planets in the galaxy. The surface temperatures of the planets in the galaxy follow...

One of the planets in the Andromeda galaxy, XNP29, has a surface temperature of 120◦K and is hotter than 33% of the planets in the galaxy. The surface temperatures of the planets in the galaxy follow a normal distribution with a standard deviation of 20◦K.
(a) Find the average surface temperature of the planets in the Andromeda galaxy.

(b) R2D2, a surface surveying robot that cannot operate at temperatures below 180◦K, can be sent for surface investigation to about how many of the 10 billion planets in the Andromeda galaxy?

 explaining them to someone who does not know anything about the subject