Is coup d’etat means overthrow?

yes

Explanation:

A coup d'état , usually shortened to coup, is the seizure and removal of a government and its powers. Typically, it is an illegal, unconstitutional seizure of power by a political faction, the military, or a dictator.

b) the confederacy had to pay all union war expenses.

worldwide, 780 million people do not have access to an improved water source. an estimated 2.5 billion people lack access to improved sanitation (more than 35% of the world's population)