Who came up with the geocentric model of the solar system?

Ptolemaic system, also called geocentric system or geocentric model, mathematical model of the universe formulated by the Alexandrian astronomer and mathematician Ptolemy about 150 CE and recorded by him in his Almagest and Planetary Hypotheses.

b - the respond is innate and varies over time.

good luck!

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.