Once you understand exactly how to perform each resistance training exercise, you should choose a weight that allows you to do how many repetitions.

This mostl depends on your goals.

If you would like to gain muscle mass and incease your size, then a repetition range of 8 to 12 repetitions is good for you.
If you would like to increase your endurance then go for more than that.
If you would like to increase your strength then go for less than that. 

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.