When you purchase an item in a store you may be charged?

mark, a civil engineer, entered into a contract with david. as per the contract, mark agreed to design and build a house for david for a specified fee. mark provided david with an estimation of the total cost and the contract was mutually agreed upon. however, during construction, when mark increased the price due to a miscalculation on his part, david refused to pay the amount. this scenario is an example of a mistake.

Why has the free enterprise system been modified to include some government intervention?

How do communism and socialism differ in terms of the role that government plays in the economy ?