Oliver is working two summer jobs, making $7 per hour washing cars and making $10 per hour clearing tables. In a given week, he can work no more than 12 total hours and must earn no less than $90. Also, he must work no less than 4 hours washing cars. If xx represents the number of hours washing cars and yy represents the number of hours clearing tables, write and solve a system of inequalities graphically and determine one possible solution.