Chapter 4 - Inverse, Exponential, and Logarithmic Functions - 4.4 Evaluation Logarithms and the Change-of-Base Theorem - 4.4 Exercises - Page 457: 43

(a) $ 2.60031933$; (b) $ 1.60031933$; (c) $ 0.60031933$; (d) see explanations.

(a) $log398.4\approx2.60031933$; (b) $log39.84\approx1.60031933$; (c) $log3.984\approx0.60031933$; (d) Shifting the decimal point 1 place to the left will reduce the common logarithms value by exactly 1. $b=a/10, log(b)=log(a/10)=log(a)-1$