Margaret earns $4500 per month. After payroll deductions from the government, Margaret takes home 75 percent of her salary. Margaret wants to use a pay yourself first method and puts $400 into her savings account before spending anything and pays $300 towards her student loans. What is Margaret's saving rate?

a)11.85 percent

b)20.74 percent

c)15.56 percent

d)8.89 percent