Rubbing a plastic rod with wool gives the plastic rod a negative charge of $8 \times 10^{-7} \ C$. How many electrons have been transferred,and from where to whom?

• A
  $5 \times 10^{10}$,from wool to plastic rod
• B
  $5 \times 10^{11}$,from plastic rod to wool
• C
  $5 \times 10^{12}$,from plastic rod to wool
• D
  $5 \times 10^{12}$,from wool to plastic rod