Mr. Gonzalez earns his living as a salary plus commission employee. His annual salary is $18,000. He makes 4% commission on all of his sales. Mr. Gonzalez wants to earn $60,000 this year. If his earnings are divided evenly throughout the year, how much in monthly sales would Mr. Gonzalez need to have?a.$37,500b.$87,500c.$100,000d.$125,000