SELECT MIN("Attendance") FROM table_75377 WHERE "Week" < '4' AND "Result" = 'w 13-7'
What is the lowest attendance that has a week less than 4, and w 13-7 as the result?
CREATE TABLE table_75377 (
    "Week" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Attendance" real
)