Mary Ann Mahler, age 12, of Ventura, Calif., for her question:

WHERE EXACTLY IS SOUTHEAST ASIA?

With a hope of being able to provide defense for the countries in Southeast Asia, a number of countries united in 1954 to form the Southeast Asia Treaty Organization, or SEATO as it was called. Australia, France, Great Britain, New Zealand, the Philippines, Thailand, Pakistan and the United States signed the Southeast Asia Collective Defense Treaty in Manila on Sept. 8, 1954. Paksitan withdrew in 1973 and the remaining members voted in 1975 to dissolve the alliance.

Southeast Asia is an important geographical location that lies south of China, east of India and north of Australia.

Included in Southeast Asia is the peninsular projection of Asia and the islands south of it. The following countries are included: Brunei, Burma, Cambodia, Laos, Malaysia, the Philippines, Singapore, Thailand, Vietnam and most of Indonesia.

Southeast Asia is the world's leading producer of natural rubber. It also is rich in petroleum, precious stones and spices. There is much forest land and excellent fishing in the area.

With the equator crossing through the territory, most of Southeast Asia is extremely tropical. The average temperature is 80 degrees Fahrenheit and the average rainfall is 40 inches. Typhoons and monsoons frequently hit and increase the annual rainfall in some places to more than 200 inches.

There are about 335 million people in Southeast Asia. Most of the mainlanders have Mongoloid ancestors, while most of the islanders are descended chiefly from Malay peoples.

The Philippines is the only Christian country in Southeast Asia. Tribal religions, Buddhism and Islam predominate.

The largest city in Southeast Asia is Jakarta, Indonesia. Other large cities, listed here in order of size, include Singapore, Singapore; Saigon, Vietnam; Bangkok, Thailand; Surabaya, Indonesia; Manila, Philippines; Bandung, Indonesia; Phnom Penh, Cambodia; Rangoon, Burma; and Semarang, Indonesia.

Thailand, Indonesia and Malaysia are among the world's leading tin producers. Also, half of the world's sapphires come from Thailand, and Malaysia is one of the leading sources of diamonds.

The forests of Southeast Asia provide the world with most of its bamboo, ebony, mahogany and sandalwood. Much pine and cedar is also produced.

During the 1960s and 1970s industry began to develop rapidly in some of the larger cities, but manufacturing remains largely undeveloped.

All of the Southeast countries grow rice, the area's main food.