Study the map and map key. Use the information in the map to answer the questions. A map titled Egyptian Trade Routes About 1450 B C shows the Egyptian Empire extending from Nubia in central Africa through upper and lower Egypt, with the following cities located on the Nile River: Nubata in Nubia, Aswan and Thebes in Upper Egypt, and Giza and Sais in Lower Egypt. The empire also extends along the eastern shores of the Mediterranean to Syria and the city of Kadesh in the north. A network of Egyptian trade routes, shown as solid black lines, connects the empire with other regions, including the city of Knossos on the island of Crete, the city of Assur on the Tigris River and the Sumer region. Trade routes also lead into Central Africa and Western Africa.

How are trade routes shown on this map?