Table: prr_locomotive_specs_2
Columns: prr_class
builder_s_model
build_date
total_produced
wheel_arrangement
service
power_output

Question: What is the total amount of freight produced of u28c?
SQL: SELECT "total_produced" FROM prr_locomotive_specs_2 WHERE "service" = 'freight' AND "builder_s_model" = 'u28c'

Question: What is the build date for PRR Class gf30a?
SQL: SELECT "build_date" FROM prr_locomotive_specs_2 WHERE "prr_class" = 'gf30a'

Question: What is the PRR class for wheel arrangement c-c and total less than 15?
SQL: SELECT "prr_class" FROM prr_locomotive_specs_2 WHERE "wheel_arrangement" = 'c-c' AND "total_produced" < 15

Question: What was the model for PRR class of gf28a freight?
SQL: SELECT "builder_s_model" FROM prr_locomotive_specs_2 WHERE "service" = 'freight' AND "prr_class" = 'gf28a'