What is the smallest value of the objective function coefficient X₁ can assume without changing the optimal solution?

MAX:	7 X1 + 4 X2
Subject to:	2 X1 + X2 16
	X1 + X2 10
	2 X1 + 5 X2 40
	X1, X2 0

Changing Cells
		Final	Reduced	Objective	Allowable	Allowable
Cell	Name	Value	Cost	Coefficient	Increase	Decrease
$B$4	Number to make: X1	6	0	7	1	3
$C$4	Number to make: X2	4	0	4	3	0.5
Constraints
		Final	Shadow	Constraint	Allowable	Allowable
Cell	Name	Value	Price	R.H. Side	Increase	Decrease
$D$8	Used	16	3	16	4	2.67
$D$9	Used	10	1	10	1	2
$D$10	Used	32	0	40	1E+30	8