user: Question: 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 4423
Columns: ['Engine type', 'Scenario', 'SFC in lb/(lbf·h)', 'SFC in g/(kN·s)', 'Specific impulse (s)', 'Effective exhaust velocity (m/s)']
Types: ['text', 'text', 'real', 'real', 'real', 'real']
Sample row: ['NK-33 rocket engine', 'Vacuum', 10.9, 309.0, 331.0, 3240.0]
SQL:

assistant: SELECT AVG("Specific impulse (s)") FROM "Table" WHERE "SFC in lb/(lbf·h)" = 7.95 AND "Effective exhaust velocity (m/s)" > 4423.0;