The Minister of Finance for the Republic of Zambia has just completed prsenting a national budget to the country's parliament for next year. In his budget address he proposed wide ranging proposals aimed at raising more domestic tax revenue through introducing new taxes as well as rationalizing the tax administration system. One of his proposals is the introduction of a unit tax of five kwacha on every mango that is supplied and consumed to the market. State and explain the principles of taxation that would be used in evaluating the newly proposed tax system.