Applying the Concept of a Production Function to Your Learning,assume

Applying the concept of a production function to your learning,assume that the amount of learning you acquire can be summarized by the following equation (and that your motivation to learn and the quality of instruction are both rated on a scale from 1 to 10) :
Amount of learning acquired = 0.2(number of books read) + 0.25(hours spent studying) + 0.15(quality of instruction) + 0.4(motivation to learn)
-Refer to Exhibit 17-5.Based on the equation given in this exhibit,if your motivation to learn rises from 7 to 9,by how much will the amount of learning acquired rise as a result?

A) 2
B) 0.8
C) 1.6
D) 8