3. Consider the following code written using Pascal syntax: var x,y: integer; (* global variables *) procedure f(a: integer, b: integer); var z: integer; begin (* f *) b; Z : = X - := a y b end; - Z; = a + 1; begin (* main *) X := 2; y : = 3; f (x + y, y); end; Describe the effect of this program on the global variables x and y, assuming: a) call by reference as the underlying mechanism for passing parameters. b) textual substitution as the underlying mechanism for passing parameters.