user: ### NOW ANSWER:
Question: How many number Builts had unit numbers of 375301-310?
Columns: ['Class', 'Type', 'Operator', 'No. Built', 'Year Built', 'Cars per Set', 'Unit nos.']
Types: ['text', 'text', 'text', 'real', 'text', 'real', 'text']
Sample row: ['Class 375/3', 'Express & Outer suburban', 'Southeastern', 10.0, '2001–2002', 3.0, '375301-310']
SQL:

assistant: SELECT SUM("No. Built") FROM "Table" WHERE "Unit nos." = '375301-310';