Consider the following linear programming problem:
Min Z = 7x1 + 5x2
Subject to:
4x1 + 3x2 ≥ 200
2x1 +x2 ≥70
x1, x2 ≥ 0

What is the upper limit of the second coefficient of the objective function (c2)?
a. 5.25
b. 3.5
c. 6.5
d. 5.5
e. none of the above