What's the model designation of the model with GVW of 2828/2.78 kg/ton and axle ratio of 9/47?
CREATE TABLE "technical_specifications" (
  "model_type" text,
  "model_designation" text,
  "engine" text,
  "wheelbase_mm_inch" text,
  "gvw_kg_ton" text,
  "axle_ratio" text
);
SELECT "model_designation" FROM "technical_specifications" WHERE "gvw_kg_ton"='2828/2.78' AND "axle_ratio"='9/47';