An object is hung from a spring, set into vertical vibration, and immersed in a beaker of oil. Its motion is graphed in Active Figure 12.14b. The object has mass 375 g, the spring has force constant 100 N/m, and the damping coefficient is b = 0.100 N·s/m. (a) How long does it take for the amplitude to drop to half its initial value? (b) How long does it take for the mechanical energy to drop to half its initial value?