The graph below depicts the demand for a commodity, in thousands, vs. selling price, in thousands of dollars. Construct a good straight-line model for this data and use your model to determine the demand at a selling price of 49 thousand dollars. Determine also the demand at which the selling price will be 40 thousand dollars . The x axis is marked in units of 15 thousand dollars and the y axis in units of 20 thousand units, both starting at (0,0).