Anna is $$10$$ years old and the age of her mother is $$4$$ times that of Anna. How old will Anna\textquotesingle s mother be when Anna\textquotesingle s mother is twice as old as Anna? (Adapted from $$2007$$ Math kangaroo Problem, Level $$5-6$$, Question \#$$20$$) 
选项为:A:$$40$$  B:$$50$$  C:$$60$$  D:$$70$$  E:$$80$$  请回答其中一个选项.