user: Question: How many constructors won the III RedeX Trophy?
Columns: ['Race Name', 'Circuit', 'Date', 'Winning driver', 'Constructor', 'Report']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Gran Premio Ciudad de Buenos Aires', 'Buenos Aires', '30 January', 'Juan Manuel Fangio', 'Mercedes', 'Report']
SQL:

assistant: SELECT COUNT("Constructor") FROM "Table" WHERE "Race Name" = 'III RedeX Trophy';