The difference between the productions of Companies X and Y in various years are:

For 1997 (139000 - 119000) = 20000.

For 1998 (120000 - 99000) = 21000.

For 1999 (141000 - 100000) = 41000.

For 2000 (128000 - 78000) = 50000.

For 2001 (120000 - 107000) = 13000.

For 2002 (159000 - 148000) = 11000.

Clearly, maximum difference was in 2000. (From the graph, we can be sure that answer is either 1999 or 2000. So we need to calculate only for those two years)

Method-2

Visually,for the year 1997, there is a difference of 1( number of rows)

For 1998, 1

For 1999, 2

For 2001, 2.5 So the highest is for 2000