202 1 How much does the promotion of rural senior teachers in Yueyang City increase every month?
On 202 1, Yueyang was promoted to a senior rural teacher, and 20 yuan was added every month. According to relevant public information, the teaching years are counted by sections from five years, and the teaching years are accumulated in 20 yuan every year, reaching 100 yuan per month in five years, 200 yuan in 10 year, 300 yuan in 15 year, 400 yuan in 20 years, and so on, 700 yuan in 35 years and 800 yuan in 40 years.