A local store sells two types of coffee beans: Arabica and Robusta. Arabica beans cost $15 per pound, and Robusta beans cost $12 per pound. A customer wants to buy a mix of beans and spend no more than $75 in total. If $a$ is the number of pounds of Arabica beans and $b$ is the number of pounds of Robusta beans the customer buys, which of the following inequalities represents this situation?