At East High School, there are a total of 1050 students in the freshman and sophomore classes. However, the freshman class has 80 more students than the sophomore class. Which system of equations could be used to determine the number of freshmen (f) and sophomores (s) in the school? Choose all that apply.

1. f + s = 1050
s + 80 = f

2. f - s = 1050
f + s = 80

3. f + s = 1050
f + 80 = s

4. f - s = 1050
s + 80 = f