Study the given table and answer the question that follows.
The given table shows the production of three types of cars (A, B and C) manufactured (in thousands) by an automobile company over the years.

Year	A	B	C
2015	840	680	890
2016	900	750	960
2017	760	620	1000
2018	800	540	1200

For all the years from 2015 to 2018, the average production of B-type cars is how much less (in thousands) than that of the combined average production of A-type and C-type cars