don't use excel or other programs, want all explanations

QUESTION 4 (20 points): In 2019, the student body at a specific university in the USA consisted of 30% freshman (year 1 students), 25% sophomores (year 2 students), 27% juniors (year 3 students), and 18% seniors (final year students). A sample of 400 students taken from the 2020 student body showed that there are 138 freshman, 88 sophomores, 94 juniors, and 80 seniors. Test with a 5% significance level to determine whether the student body proportions have changed 7 A v B PA