Several forms of gasoline are produced during the petroleum refining process, and a last step combines them to obtain market products with specified quality measures. Suppose 4 different gasolines are available, with values for the 2 indexes of quality being 99 and 210, 70 and 335, 78 and 280, and 91 and 265, respectively.

Using corresponding costs per barrel of

$48, $43, $58, and $46, we would like to choose a minimum cost blend with a first quality index between 85 and 90 and a second index between 270 and 280.

(a) Formulate a blending LP to choose an optimal gasoline blend.

(b) Which of the constraints of your model are composition constraints? Explain.

(c) Enter and solve your model with the class optimization software.