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

### Instruction:
what is the average specific impulse for engines that have a SFC in lb/(lbf·h) of 7.95, and a Effective exhaust velocity (m/s) larger than 4,423

### Inputs:
table_name: table, columns: ['Engine type', 'Scenario', 'SFC in lb/(lbf·h)', 'SFC in g/(kN·s)', 'Specific impulse (s)', 'Effective exhaust velocity (m/s)']

### Response:
SELECT AVG Specific impulse (s) FROM table WHERE SFC in lb/(lbf·h) = 7.95 AND Effective exhaust velocity (m/s) > 4,423