Suppose that the sound level of a conversation is initially at an angry 74 dB and then drops to a soothing 50 dB. Assuming that the frequency of the sound is 516 Hz, determine the (a) initial and (b) final sound intensities (in ?W/m2) and the (c) initial and (d) final sound wave amplitudes (in nm). Assume the speed of sound is 347 m/s and the air density is 1.21 kg/m3.