A command economy tends to exist under a

Geologists know that potassium-40 decays to argon-40, with a half-life of 1.3 billion years. if an analysis of a feldspar crystal in a sample of granite shows that 75 percent of the potassium-40 atoms have decayed to form argon-40, what is the age of the granite

What are the 28 countries in the eu?

What empire controlled most of the middle east except for a few years between 1516 and 1917, where was the capital of this empire located and what was the geographic extent of this empire?