Which sentences use a semicolon correctly?

henry j. kaiser, a steelmaker and shipbuilder, originally conceived the idea for the new prototype; however, howard hughes and his staff are credited with the actual design and construction of the craft.

by this time, the government had spent an estimated $22 million on the project; hughes had personally spent $18 million of his own money.

naismith had to think of something that would encourage everyone to play; and keep him active without being too rough with each other.

using his vast experience with other sports games, naismith took bits and pieces of each; in order to meet the parameters he was given.

always active in athletics and team sports, naismith created the game of basketball to emphasize athletic skill; while shifting the focus away from the rough play of other popular games such as football and rugby.