I need help with my statistics homework. I have about 6 questions. Can someone please help?

1. Find the probability of obtaining exactly 2 heads in 4 tosses of a fair coin? Also find the mean and variance. This is an experiment with replacement.

2. The weight of a grapefruit from a large shipment averages 15 oz. with a standard deviation of 2 oz. If these weights are normally distributed and if a grapefruit is picked at random, what is the probability that it will weigh between 13 and 14 oz.?

3. If an urn contains 4 green balls and 3 black balls what is the probability of drawing 3 black balls in a sample size 3 drawn without replacement?

4. Records indicate that 30 % of all students on a university campus are female. Also, 20% of the females are "A" students, plus 70% of the males are "A" students. If an "A" student is selected at random, whta is the probability that the student is female?

5. Two cards are drawn from a deck of 52 cards. Calculate the probability that the draw will include an ace and a nine.

6. A sample of 49 units are taken randomly from a batch of items. The mean cost per unit is $10 with a standard deviation of $3. Construct the 92% confidence interval estimate for M.

Thank you.