Table: pratt_whitney_r_985_2
Columns: engine
power_continuous
power_takeoff
compression_ratio
supercharger_gear_ratio
octane_rating
dry_weight

Question: Which supercharger gear ratio has a Octane rating of 68?
SQL: SELECT "supercharger_gear_ratio" FROM pratt_whitney_r_985_2 WHERE "octane_rating" = '68'