A linear programming problem is shown below.
Maximize 3x + 7y
Subject to 3x+ 7y $\leq$ 10
4x + 6y $\leq$ 8
x, y $\geq$ 0
It has…………
(a) an unbounded objective function
(b) exactly one optimal solution
(c) exactly two optimal solutions
(d) infinitely many optimal solutions