Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_66 (firefox VARCHAR, safari VARCHAR)
### Question:
What percentage of users were using Firefox according to the source that reported 15.40% used Safari?
### Answer:
SELECT firefox FROM table_name_66 WHERE safari = "15.40%"