There are three red balls and seven white balls in box A, and six red balls and four white balls in box B. After throwing a die, if the number on the die is 1 or 6, then pick a ball from box A. Otherwise, if any other number appears (i.e., 2, 3, 4, or 5), then pick a ball from box B. Selected ball has to put it back before proceeding further.

(a) What is the probability that the selected ball is red?
(b) What is the probability a white ball is picked up in two successive selections?