In 10 boxes of marbles there are 4 boxes of type 1, each box has 4 white marbles and 4 red marbles. 3 boxes of type 2, each box has 3 white marbles and 7 red marbles. 3 boxes of type 3, each box has 3 white balls and 4 red marbles. Randomly draw a box and then draw a ball at random. Find the probability that the ball is white.
