CREATE TABLE table_39991 ("Gill" TEXT, "Latitude" TEXT, "Longitude" TEXT, "Diameter  ( km ) " TEXT, "Diameter  ( mi ) " TEXT)

What is the Diameter (mi) when the Longitude is 79.8 e?
SELECT "Diameter (mi)" FROM table_39991 WHERE "Longitude" = '79.8° e'
SELECT "Diameter (mi)" FROM "table_39991" WHERE "Longitude" = '79.8° e'