Which of the following are correct in respect of graphically solved linear programming problems?
1. The region of feasible solution has concavity property.
2. The boundaries of the region are lines or planes.
3. There are corners or extreme points on the boundary
Select the correct answer using the code given below:
(a) 1 and 2 (b) 2 and 3
(c) 1 and 3 (d) 1, 2 and 3