Passage: The area of Java is approximately 150,000 square kilometres (58,000 sq mi). It is about 1,000 km (620 mi) long and up to 210 km (130 mi) wide. The island's longest river is the 600 km long Solo River. The river rises from its source in central Java at the Lawu volcano, then flows north and eastward to its mouth in the Java Sea near the city of Surabaya. Other major rivers are Brantas, Citarum, Cimanuk and Serayu.

Question: What is the longest river on the Java Island
Solo River