The monthly wages of a sample of $100$ employees were recorded and the numbers are rounded to the nearest ten dollars. They are arranged from $\$1,040$ to $\$1,720$.
Which of the following statements are the most appropriate in constructing a frequency distribution for this set of data?
i. the number of classes should be 7.
ii. the class interval should be \$100.
iii. the number of classes should be 6.
iv. the class interval should be \$90.