The school planted 500 trees last spring, the survival rate was 85%, and the survival rate last autumn was 90%. It is known that 20 more trees were planted last spring than in autumn. How many trees were planted in the school last autumn?
学校去年春季栽树500棵，成活率85%，去年秋季的成活率为90%．已知去年春季比秋季多活了20棵数，去年秋季学校共种活了多少棵树？
<result>403</result>