A weather forecaster predicts that the May rainfall in a local area will be between three and six inches but has no idea where within the interval the amount will be. Let x be the amount of May rainfall in the local area, and assume that x is uniformly distributed over the interval three to six inches.

a. Write the formula for the probability curve of x and graph this probability curve.

b. What is the probability that May rainfall will be at least four inches? At least five inches?