Of all the students in a certain dormitory, ~$1 \over 2$~are first-year students and the rest are second-year students. If ~$4 \over 5$~ of the first-year students have not declared a major and if the fraction of second-year students who have declared a major is 3 times the fraction of first-year students who have declared a major, what fraction of all the students in the dormitory are second-year students who have not declared a major?