According to Franchise Business Review, over 50% of all food franchises earn a profit of less than $50,000 a year. In a sample of 142 casual dining restaurants, 81 earned a profit of less than $50,000 last year.

a. What is the point estimate of the proportion of casual dining restaurants that earned a profit of less than $50,000 last year?
b. Determine the margin of error and provide a 95% confidence interval for the of casual dining restaurants that earned a profit of less than $50,000 last year.
c. How large a sample is needed if the desired margin of error is .03?