The Green Giant has a $5\%$ profit margin and a $40\%$ dividend payout ratio. The total asset turnover is $1\mathrm{.}40$ and the equity multiplier is $1\mathrm{.}50.$ What is the sustainable rate of growth?

a$.6\mathrm{.}53\%$

b$.6\mathrm{.}80\%$

c$.6\mathrm{.}83\%$

d$.6\mathrm{.}30\%$

e$.6\mathrm{.}72\%$