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7.5b Log-bimodal size distribution An aerosol population results from the combination of particulate matter from two distinct sources. The coarser source is log-normally distributed with MMD=10m and g=3.0. The finer source is also log-normally distributed with g=2.5, but unknown MMD. Twenty-three percent of all the mass originates at the fine particle source. It was found experimentally that the combined, cumulative mass fraction up to 3m was 30.8%. Estimate the value of MMD for the fine source