1. A computer-readable, non-transitory storage medium storing a program for causing a computer to execute a procedure, the procedure comprising: connecting an approximate expression of a cost function representing a relationship between a plurality of design parameters and a cost, a route in a cost space and a search range in a design parameter space with logical conjunctions to generate a constraint equation; obtaining a logical expression of a solution for the constraint equation from a quantifier elimination processing unit that carries out a processing according to a quantifier elimination method; substituting coordinates of each of a plurality of points within the search range in the design parameter space into the logical expression of the solution to determine, for each of the plurality of points, true or false of the logical expression of the solution; and displaying a design parameter space in which a display object including a first point for which true is determined among the plurality of points, is disposed at the first point.