Continuous Probability Distributions

For a certain lake, baseline measurements of acidity are made so that any changes caused by acid rain can be noted. The pH for water samples from the lake is a random variable X with probability density function:

http://i44.tinypic.com/30rod55.jpg

a) Sketch the curve of f(x)

b) Find the distribution function F(x) for X

c) Find the probability that the pH for a water sample from this lake will be less than 6

d) Find the probability that the pH of a water sample from this lake will be less than 5.5 given that it is known to be less than 6

Can anyone help me with this? My textbook doesn't give any examples like this, and I have no idea what to do.