Susan starts an electric bicycle company with her savings of $$200,000.$ Her new business is successful, and she attracts a $$2$ million investment from venture capital firm A at a post$-$money valuation of $$5$ million. Susan continues to grow her business and meets additional milestones. After seeing that the milestones have been met, venture capital firm A and a new venture capital firm, B$,$ invests a combined $$15$ million into Susan$$s electric bicycle firm at a post$-$money valuation of $$40$ million. What is Susan$$s ownership of the firm after this investment?