The 2011 gross sales of all companies in a large city have a mean of $2.3 million and a standard deviation of $.6 million. Using Chebyshev’s theorem, find at least what percentage of companies in this city had 2011 gross sales of
a. $1.1 to $3.5 million
b. $.8 to $3.8 million
c. $.5 to $4.1 million