12.46 An aircraft company wanted to predict the number of worker-hours necessary to finish the design of a new plane. Relevant explanatory variables were thought to be the plane’s top speed, its weight, and the number of parts it had in common with other models built by the company. A sample of 27 of the company’s planes was taken, and the following model was estimated:

y = b0 + b1x1 + b2x2 + b3x3 + e where y = design effort, in millions of worker-hours x1 = plane’s top speed, in miles per hour x2 = plane’s weight, in tons x3 = percentage number of parts in common with other models The estimated regression coefficients were as follows:

b1 = 0.661 b2 = 0.065 b3 = -0.018 and the estimated intercept was 2.0.

Predict design effort for a plane with a top speed of Mach 1.0, weighing 7 tons, and having 50% of its parts in common with other models.