6. Choose the correct inequation

Hendry is a salesperson, earns $₹$2000 for every bike he sell and $₹$3500 for every car he sells as an incentives. He earns $₹$15000 per month as a salary, including incentives.

 

Take $a$ as the number of bikes he sells and $b$ as the number of cars he sells, then select the correct inequation that explains the perfect relation between his salary and incentives.