In a Linear Programming Problem,the Binding Constraints for the Optimal

In a linear programming problem,the binding constraints for the optimal solution are
5x + 3y  30
2x + 5y  20
a.Fill in the blanks in the following sentence:As long as the slope of the objective function stays between _______ and _______, the current optimal solution point will remain optimal.
b.Which of these objective functions will lead to the same optimal solution?1) 2x + 1y 2) 7x + 8y 3) 80x + 60y 4) 25x + 35y