13. [Deferred taxes and interm reports] State Auto Financial [STFC] reported the following operating results for the first three quarters of 1991 and 1992 (S in thousands): 1991 QI Q2 Q3 Pretax income $4.797 $2,600 $3,244 Income tax expense (1.224) (624) (848) Net income $3.573 $1,976 $2,396 1992 QI Q2 Q3 Pretax income Income tax expense Net income $1.123 $3,723 $ 98 (232) (934) 583 $ 891 $2,789 $681 State Auto's 1992 third-quarter 10-Q reported that the estimated annual effective tax rate was revised during the third quarter of 1992 from 25% to 17% to reflect the estimated tax impact of a decrease in taxable earnings, as prescribed by generally accepted accounting principles. The effect of this adjustment in the current quarter was a benefit of approximately $600,000.

a. Compute the tax rate used to compute net income for cach quarter.