Refer to Exercises 12-1 and 12-2. Suppose you believe that the impact of contract cost on web development time is dependent on the type of industry that the company is from.

(a) What is the model equation in this context?

(b) What null hypothesis would you test to determine that the nature of the impact of contract cost on web development time does not depend on the type of industry?

(c) Based on historical data, you believe that web development time increases at a faster rate as the contract cost increases. Write down the equation of the model.