Obtain a plot of the data of Exercise 11.90, with durability on the vertical axis and ­concentration on the horizontal axis.
a. What does this plot indicate about the wisdom of using straight- line prediction?
b. What does this plot indicate about the correlation found in Exercise 11.90?
In exercise

Conc. 20 20 20 20 20 20 20 20 20 2020 20 Durab. 533 252 49 20.3 55.5 50.7 57.1 34 52.7 42.5 51.7 47.0 Conc. 30 30 30 30 30 30 30 330 30 30 30 Durab. 67.2 66.7 56.7 60.3 68.0 56. 59.9 63.3 64.4 49.3 61.7 62.3 Conc. 40 40 40 40 40 40 40 40 40 40 4040 Durab 64.7 68,0 76.5 69.9 691 50.7 571 65.7 67. 744 73.5 69.9 Conc. 50 50 50 5050 50 50 50 50 5050 Durab. 516 75.7 55.9 76 55.3 73.3 615 53.3 74473.6 76.5 73.3 Conc 60 60 06060 60 60 6060 60 60 60 Durab. 58.7 705 52.5 59.9 65.9 63.3 64.9 53.6 52.5 63.8 59.7 58.9