Consider the following binary linear programming formulation of a capital budgeting problem.

\[\begin{array}{ll}\text { Max } & 1,200 x_{1}+600 x_{2}+950 x_{3}+1,650 x_{4} \\\text { s.t. } & 15,000 x_{1}+20,000 x_{2}+25,000 x_{3} \\& +30,000 x_{4}<=70,000 \\& x_{1}+x_{2}<=1 \\& x_{4}<=x_{3} \\& x_{1}, x_{2}, x_{3}, x_{4}=(0,1)\end{array}\]

The capital budget limit is

a. \(\$ 90,000\).

b. \(\$ 70,000\).

c. \(\$ 30,000\).

d. \(\$ 4,400\).