What's the model designation of the model with GVW of 2828/2.78 kg/ton and axle ratio of 9/47?
create table table_20866024_3 (model_designation varchar, gvw__kg_ton_ varchar, axle_ratio varchar, PRIMARY KEY (model_designation))
select model_designation from table_20866024_3 where gvw__kg_ton_ = "2828/2.78" and axle_ratio = "9/47"