probability word problem help, please....

**Ok, I have 3 word problems dealing with probability that I need help with. So here they are:(Wondering)**

**1.Suppose a contest offers $1,000 to the person who can guess the winning 4 digit number. How many possibilities are there?**

**2. Two marbles are drawn froma bag containing 6 white, 4 red, and 6 green marbles. Find the probability of both marbles being white.**

**3. Suppose there are 10 items on a true-false test. The person taking the test does not read the questions; he just answers each question randomly. What is the probability of his guessing all answers correctly?**

**Thanks in advance for any help!**