user: Question: How much did the Modern pentathlon III series coin weigh?
Columns: ['Year', 'Denomination', 'Alloy', 'Reverse', 'Diameter', 'Weight', 'Obverse', 'Mintage', 'Series']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: [2007.0, '1 Yuan', 'Brass', 'Weightlifting', '25mm', '6.75 gr', 'Emblem of the XXIX Olympiad, and the year 2008.', 10000000.0, 'I series']
SQL:

assistant: SELECT "Weight" FROM "Table" WHERE "Series" = 'III series' AND "Reverse" = 'Modern pentathlon';