If $8 \%$ of the people eligible to vote are between $18$ and $21$ years of age,and in an election,$85 \%$ of those eligible to vote who were between $18$ and $21$ years of age actually voted,then the number of persons between $18$ and $21$ years of age who actually voted is what percent of the total people eligible to vote?

• A
  $4.2$
• B
  $6.4$
• C
  $6.8$
• D
  $8$