What causes ocean water around the equator to be warmer then the ocean water farther south of the equator

a. gyres in the northern hemisphere flow clockwise.
b. upwellings spew warm water toward the equator.
c. the sun heats earth and it’s oceans unevenly.
d. deep sea vents pump stream into oceans unevenly.

Two identical stars with mass m orbit around their center of mass. each orbit is circular and has radius r, so that the two stars are always on opposite sides of the circle. (a) find the gravitational force of one star on the other. (b) find the orbital speed of each star and the period of the orbit. (c) how much energy would be required to separate the two stars to infinity?