What is the dual problem for given linear programming problem? Z = Max (4x1 + 5x2 + 7x3) s.t. 3x1 + x2 + 6x3  <= 3 x1 + 2x2 + x3 <= 4 x1, x2, x3 >= 0
a)    Z = Min (3y1 + 4y2) s.t 3y1 + y2 >= 4 y1 + 2y2 >= 5 6y1 + 3y2 >= 7 y1, y2 >= 0
b)    Z = Min (3y1 + 4y2) s.t 3y1 + y2 >= 4 y1 + 2y2 <= 5 6y1 + 3y2 >= 7 y1, y2 >= 0
c)    Z = Min (3y1 + 4y2) s.t 3y1 + y2 <= 4 y1 + 2y2 >= 5 6y1 + 3y2 <= 7 y1, y2 >= 0
d)    Z = Max (3y1 + 4y2) s.t 3y1 + y2 >= 4 y1 + 2y2 >= 5 6y1 + 3y2 >= 7 y1, y2 >= 0
e)    None of these