4 (b) 4.0(8.0)z = 7.0(3.0)z-1
log 4.0 + z log 8.0 = log 7.0 + (z - 1) log 3.0
0.602 + 0.903 z = 0.845 + 0.477 (z - 1)
0.602 + 0.903 z = 0.845 + 0.477 z - 0.477
0.426 z = -0.234
z = -0.55 (2 sig. fig)

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