Please answer the following question: How many acres is the larger ecosystem that park located in the northwestern region is a part of?  Answer the above question based on the context below:  Grand Teton National Park is located in the northwestern region of the U.S. state of Wyoming. To the north the park is bordered by the John D. Rockefeller, Jr. Memorial Parkway, which is administered by Grand Teton National Park. The scenic highway with the same name passes from the southern boundary of Grand Teton National Park to West Thumb in Yellowstone National Park. Grand Teton National Park covers approximately 310,000 acres (130,000 ha), while the John D. Rockefeller, Jr. Memorial Parkway includes 23,700 acres (9,600 ha).  Most of the Jackson Hole valley and virtually all the major mountain peaks of the Teton Range are within the park. The Jedediah Smith Wilderness of Caribou-Targhee National Forest lies along the western boundary and includes the western slopes of the Teton Range. To the northeast and east lie the Teton Wilderness and Gros Ventre Wilderness of Bridger-Teton National Forest. The National Elk Refuge is to the southeast, and migrating herds of elk winter there. Privately owned land borders the park to the south and southwest. Grand Teton National Park, along with Yellowstone National Park, surrounding National Forests and related protected areas constitute the 18,000,000-acre (7,300,000 ha) (28,000 sq mi (73,000 km2)) Greater Yellowstone Ecosystem. The Greater Yellowstone Ecosystem spans across portions of three states and is one of the largest intact mid-latitude ecosystems remaining on Earth. By road, Grand Teton National Park is 290 mi (470 km) from Salt Lake City, Utah and 550 mi (890 km) from Denver, Colorado.
Answer:
18,000,000