, given constraints x-ygreater than or equal to -2 x+y greater than or equal to -4 and 2x-y less than or equal to 4

Problem is not given correctly.

L = 0.5 - 0.3y

This is a linear function its domain is ( -∞, + ∞) minimum value of y can be infinitely large, multiplied by

-0.3 can be infinitely small number, and so does L.