An operations research analyst is investigating the relationship between production lot size x and the average production cost per unit y . A study of recent operations provides the following data:

x 100 120 140 160 180 200 220 240 260 280 300 y $9.73 9.61 8.15 6.98 5.87 4.98 5.09 4.79 4.02 4.46 3.82 The analyst suspects that a piecewise linear regression model should be fi t to these data. Estimate the parameters in such a model assuming that the slope of the line changes at x = 200 units. Do the data support the use of this model?