急！prepare两道题。。。麻烦各位帮忙。。。周三就考了

甜心俏女巫

1.  Each of the 25 balls in a certain box is either red, blue or white has a number from 1 to 10 painted on it. I one ball is to be selected at random from the box, what's the possibility of the ball selected will either be white or have an even number painted on it?
(1) The probability that the ball will both be white and have an even number painted on it is 0.
(2) The probability that the ball will be white minus the probability that the ball will have an even number painted on it is 0.2.

2. A certain stock exchange designates eacch stock with a one-,two-,or three-letter code, where each letter is selected from the 26 letters of the alphabet. If the letters may be repeated and if the same letters used in a different order constitute a different code, how many different stocks is it possible to uniquely designate with these codes?
A2951   B8125   C15600   D16302   E18278

麻烦各位解释下题。。。再分析下。。。万分感激。。。

甜心俏女巫

不好意思第一题还是为看懂。。。能不能麻烦再解释下呀？谢谢