def main(input):
    output = []
    for row in input:
        sold, returned = int(row["sold_units"]), int(row["returned_units"])
        invalid = sold < 0 or returned < 0 or returned > sold
        rate = round(returned / sold * 100, 2) if sold > 0 and not invalid else ""
        status = ("invalid_cohort" if invalid else "no_sales" if sold == 0
            else "high_returns" if rate >= 8 else "ok")
        output.append(dict(row, return_rate_pct=rate, return_status=status))
    return output