CREATE TABLE table_54802 ("PRR Class" TEXT, "Builderpars_m_singles Model" TEXT, "Build date" TEXT, "Total produced" FLOAT, "Wheel arrangement" TEXT, "Service" TEXT, "Power output" TEXT)

What was the model for PRR class of gf28a freight?
SELECT "Builder\u2019s Model" FROM table_54802 WHERE "Service" = 'freight' AND "PRR Class" = 'gf28a'
SELECT "Builder\u2019s Model" FROM "table_54802" WHERE "PRR Class" = 'gf28a' AND "Service" = 'freight'