What is the average SFC in lb/(lbf·h) for engines with an Effective exhaust velocity (m/s) larger than 29,553, and a SFC in g/(kN·s) of 17.1?
CREATE TABLE "specific_fuel_consumption_sfc_specific_i" (
  "engine_type" text,
  "scenario" text,
  "sfc_in_lb_lbf_h" real,
  "sfc_in_g_k_n_s" real,
  "specific_impulse_s" real,
  "effective_exhaust_velocity_m_s" real
);
SELECT AVG("sfc_in_lb_lbf_h") FROM "specific_fuel_consumption_sfc_specific_i" WHERE "effective_exhaust_velocity_m_s">'29,553' AND "sfc_in_g_k_n_s"=17.1;