Correct Answer: 6.6

Solution : We know the formula, Average = $\frac{\text{Sum of all values}}{\text{The total of all values}}$
The average income of all the companies = $\frac{55+50+35+40+60}{5}=\frac{240}{5}$
The average expenditure of all the companies = $\frac{50+40+32+35+50}{5}=\frac{207}{5}$
The difference between the average income and average expenditure of all the companies
$=\frac{240}{5}-\frac{207}{5}=\frac{33}{5}=6.6$
Hence, the correct answer is 6.6.