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An investment portfolio contains stocks of a large number of corporations. Over the last year the rates of return on these corporate stocks followed a normal distribution with mean 10.3% and standard deviation 4.6%. a. For what proportion of these corporations was the rate of return higher than 16% ? b. For what proportion of these corporations was the rate of return negative? c. For what proportion of these corporations was the rate of return between 5% and 15% ? Click the icon to view the standard normal table of the cumulative distribution function. a. The proportion of corporations whose rate of return was higher than 16% is (Round to four decimal places as needed.) An investment portfolio contains stocks of a large number of corporations. Over the last year the rates of return on these corporate stocks followed a normal distribution with mean 10.3% and standard deviation 4.6%. a. For what proportion of these corporations was the rate of return higher than 16% ? b. For what proportion of these corporations was the rate of return negative? c. For what proportion of these corporations was the rate of return between 5% and 15% ? Click the icon to view the standard normal table of the cumulative distribution function. a. The proportion of corporations whose rate of return was higher than 16% is (Round to four decimal places as needed.)