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The Federal Reserve System publishes data on family income based on its Survey of Consumer Finances. When the head of the household has a college degree, the mean before-tax family income is $84,600. Suppose that 56% of the before-tax family incomes when the head of the household has a college degree are between $74,700 and $94,500 and that these incomes are normally distributed. What is the standard deviation of before-tax family incomes when the head of the household has a college degree? (Round the volue of z to 2 decimal places, e.s. 1.29. Round your answer to 2 decimfli places, e.s. 125.31.)