Climate: Varies with altitude; humid and tropical to cold and semiarid. Terrain: Rugged Andes Mountains with a highland plateau (Altiplano), hills, lowland plains of the Amazon Basin. Elevation extremes: Lowest point: Rio Paraguay 90 m Highest point: Nevado Sajama 6,542 m Economy: Bolivia, long one of the poorest and least developed Latin American countries, has made considerable progress toward the development of a market-oriented economy. Successes under President SANCHEZ DE LOZADA (1993-97) included the signing of a free trade agreement with Mexico and becoming an associate member of the Southern Cone. Common Market (Mercosur), as well as the privatization of the state airline, telephone company, railroad, electric power company, and oil company.