user: Question: What was the combined weight in kilograms of the horses in the race at chelmsford stakes?
Columns: ['Result', 'Date', 'Race', 'Venue', 'Group', 'Distance', 'Weight (kg)', 'Time', 'Jockey', 'Winner/2nd']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'real', 'text', 'text', 'text']
Sample row: ['Won', '23 Aug 2003', 'Warwick Stakes', 'Warwick Farm', 'G2', '1400 m', 58.0, '1:24.35', 'D. Beadman', '2nd - Clangalang']
SQL:

assistant: SELECT SUM("Weight (kg)") FROM "Table" WHERE "Race" = 'chelmsford stakes';