Tracey's works for a furniture store and earns a salary plus a commission based on sales. the equation below represents y, tracey's earnings in a week when she sells x dollars' worth of furniture. y=0.05x + 300. what happens to tracey's weekly earnings as the sales increase by $800? a.) increase by $15.00 b.) increase by $25.00 c.) increase by $40.00 d.) increase by $55.00