user: Question: What is the average SFC in lb/(lbf·h) for engines with an Effective exhaust velocity (m/s) larger than 29553, and a SFC in g/(kN·s) of 17.1?
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("SFC in lb/(lbf·h)") FROM "Table" WHERE "Effective exhaust velocity (m/s)" > 29553.0 AND "SFC in g/(kN·s)" = 17.1;