The following tables each show the inventory of a warehouse and the number of orders for four different products which have been shipped out to customers. which table best represents a linear relationship?

Orders: x
Inventory: y

1) First table
x2-x1=6-3→x2-x1=3
y2-y1=1920-1960→y2-y1=-40

x3-x2=9-6→x3-x2=3=x2-x1
y3-y2=1900-1920→y3-y2=-20 different to y2-y1=-40. The table does not represent a linear relationship.

2) Second table
x2-x1=7-5→x2-x1=2
y2-y1=1860-1900→y2-y1=-40

x3-x2=9-7→x3-x2=2=x2-x1
y3-y2=1820-1860→y3-y2=-40=y2-y1

x4-x3=11-9→x4-x3=2=x3-x2
y4-y3=1780-1820→y4-y3=-40=y3-y2

x5-x4=13-11→x5-x4=2=x4-x3
y5-y4=1740-1780→y5-y4=-40=y4-y3

The table represents a linear relationship.

3) Third table
x2-x1=2-1→x2-x1=1
y2-y1=1000-2000→y2-y1=-1000

x3-x2=3-2→x3-x2=1=x2-x1
y3-y2=500-1000→y3-y2=-500 different to y2-y1=-1000. The table does not represent a linear relationship.

4) Fourth table
x2-x1=6-4→x2-x1=2
y2-y1=1640-1840→y2-y1=-200

x3-x2=8-6→x3-x2=2=x2-x1
y3-y2=1360-1640→y3-y2=-280 different to y2-y1=-200. The table does not represent a linear relationship.

The second table best represents a linear relationship.