Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_204_681 ( id number, "2011 rank" number, "2010 rank" number, "2009 rank" number, "2008 rank" number, "2007 rank" number, "company (country)" text, "2011 arms sales (us$ m.)" number, "2010 arms sales (us$ m.)" number, "2009 arms sales (us$ m.)" number, "2008 arms sales (us$ m.)" number, "2007 arms sales (us$ m.)" number, "arms sales as share of company's total sales (%)," number )

### Question ###
what is the difference of the amount sold between boeing and general dynamics in 2007 ?

### Accurate SQL ###

SELECT ABS((SELECT "2007 arms sales (us$ m.)" FROM table_204_681 WHERE "company (country)" = 'boeing') - (SELECT "2007 arms sales (us$ m.)" FROM table_204_681 WHERE "company (country)" = 'general dynamics'))