18. How is the income tax expense for the third quarter interim period computed? A. The annual rate multiplied by the third quarter pretax earnings B. The estimated tax rate for the first three quarters based on annual rate, less a similar estimate for the first two quarters C. The rate applicable during the third quarter multiplied by four times the third quarter pretax earnings D. One-half of the difference between total estimated annual income tax expense and the income tax for the first two quarters