The internal economy refers to the increase in the internal revenue caused by a manufacturer when the production scale expands, while the external economy refers to the increase in the revenue brought to individual manufacturers by the expansion of the entire industry. According to the above definition, which of the following is external economies? ['The rare earth industry has developed rapidly in recent years. Due to the reduction in transportation costs and tariffs, some mining companies have continued to increase their exports and established trade relations with many countries.', 'Due to the introduction of a number of advanced equipment, a tea manufacturer has increased its production efficiency, and its sales volume has doubled compared with previous years.', 'The domestic mobile phone industry is developing rapidly and the scale is constantly expanding. In order to enhance the competitiveness of its products, a mobile phone manufacturer began to streamline its organization and reduce costs.', 'Due to the rising international oil prices, gas stations in some areas of Guangdong Province have made more profits by raising prices.']