An urn A contains 8 black balls and 5 white balls. A second urn B contains 6 black and 7 white balls. The probability that a blind folded person in one draw shall obtain a white ball

• A

  $\frac{\text{5}}{13}$

• B

  $\frac{\text{7}}{13}$

• C

  $\frac{\text{6}}{13}$

• D

  $\frac{\text{5}}{26}$