Ben swims​ 50,000 yards per week in his practices. Given this amount of​ training, he will swim the​ 100-yard butterfly in seconds and place th in a big upcoming meet. ​ Ben's coach calculates that if Ben increases his practice to​ 60,000 yards per​ week, his time will decrease to seconds and he will place th in the meet. If Ben practices​ 70,000 yards per​ week, his time will be seconds and he will win the meet. In terms of​ Ben's time in the big​ meet, what is his marginal productivity of the number of yards he​ practices? The marginal product of increasing practice yards from​ 50,000 to​ 60,000 is nothing ​second(s) ​(enter a numeric response using a real number rounded to one decimal​ place)