Calculate the mean scattering cross-section at a frequency of 5 MHz of a distribution of air bubbles of 3 μm mean radius, assuming a Gaussian size distribution of a variance of 1 μm and 1.5 μm. The total damping constant is 1.0. The total number of air bubbles is 100,000. Repeat these calculations at 4 MHz and 6 MHz for variance = 1 μm. Discuss the effects of size distribution and bandwidth on the mean scattering cross-section.