Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
With what type of chambering is the F bolt n (lbf) and the P max (bar) 3900?

### Inputs:
table_name: table, columns: ['Chambering', 'P1 diameter (mm)', 'A external (cm 2 )', 'P max ( bar )', 'F bolt ( kgf )', 'F bolt']

### Response:
SELECT Chambering FROM table WHERE F bolt = N (lbf) AND P max ( bar ) = 3900