user: Question: Name the number for service dates for Hoosier Energy for Petersburg
Columns: ['Name', 'Location', 'Act. Units', 'Stacks', 'In Service Dates', 'Unit Capacity (2009)', 'Nameplate Capacity (2009 MW )', 'Owner Type', 'Owner(s) (2009)']
Types: ['text', 'text', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['A.B. Brown', 'Posey Co. / Vand. Co.', 4.0, '4', '1 1979 2 1986 3 1991 4 2002', '1 & 2 235 MW 3 & 4 88.2 MW', '707', 'Large Corporation', 'Vectren']
SQL:

assistant: SELECT "In Service Dates" FROM "Table" WHERE "Owner(s) (2009)" = 'Hoosier Energy' AND "Location" = 'Petersburg';