Table:
Combined Pension Plan

Years Ended December 31,

2019	2018	2017

(Dollars in millions)

Change in benefit obligation

Benefit obligation at beginning of year	$11,594	13,064	13,244

Service cost	56	66	63

Interest cost	436	392	409

Plan amendments	(9)	—	—

Special termination benefits charge	6	15	—

Actuarial (gain) loss	1,249	(765)	586

Benefits paid from plan assets	(1,115)	(1,178)	(1,238)

Benefit obligation at end of year	$12,217	11,594	13,064

How many rows and columns does this table have? Output the final answer in the JSON format {"row_number": "m", "column_number": "n"}. For instance, if the table has 5 rows and 4 columns, the answer would be {"row_number": "5", "column_number": "4"}

There are 13 rows and 4 columns in the table. So, the final answer is {"row_number": "13", "column_number": "4"}.