Emissions of sulfur dioxide by industry set off chemical changes in the atmosphere that result in "acid rain". the acidity of liquids is measured by ph on a scale of 0 to 14. distilled water has ph 7.0, and lower ph values indicate acidity. normal rain is somewhat acidic, so "acid rain" is sometimes defined as rainfall with a ph below 5.0. the ph of rain at one location varies among rainy days according to a normal distribution with mean 5.43 and standard deviations 0.54. what proportion of rainy days have rainfall with ph below 5.0?