Business statistics: Mean, Standard Deviations

I could use some help with the following. Could you please explan how you get the answer to the following questions in detail please so I can compare them to mine. I am not understanding my book very well and I want to make sure I am understanding them correctly before I turn them in. Thank you

My first question is;
The mean starting salary for college graduates in the spring of 2004 was $36,280.
I am ask to assume the distribultion of starting salaries follows the normal distraibution with a standard deviation of $3,300.
What percentage of the graduates have starting salaries?
a) Between $35,000 and 45,000
b) More than $45,000
c) Between $40,000 and 45,000

My second question is;
I am ask to assume a binomial probabitity distribution with n=40 and  (pi) =.55 and compute the folowing
a) The mean and standard deviation of random variable
b) The probability that X is 25 or greater
c) The probability that X is 15 or less
d) The probability that X is between 15 and 25 inclusive

My third question;
A resent study by the Greater Los Angeles Taxi Drivers Association showed that the mean fare charged for service from Hermosa Beach to the Los Angeles International Airport is $18.00 and the standard deviation is $3.50.
I am ask to select a sample of 15 fares and answer a and b. Please explain how you got your answer so I can compare it to mine.
a) What is the likelihood that the sample mean is is btw $17.00 and 20.00?
b) What must you assume to make the above calculation?

My last question;
Dr Patton is a Professor of English. Recently he counted the number of misspelled words in a group of students essays. For his class of 40 students, the mean number of misspelled words was 6.05 and the standard deviation 2.44 per essay.
I need help constructing a 95 percent confidence interval for the mean number of misspelled words in the population of student essays.