15. [Global Dptimizatitu Find the global maximum and minimum valuu-i of the function on the given domain. Be sure to do the following: 11 n - Check for any critical points in the interior of the domain 0 Check for any critical points on the houndmy curves of the domain (using paraJnetrization} In Check the value of the function at the endpoints of the boundary elm (a) f(.r,y} = 2 + y: on the triangular region whose vertiocs an: (31D). (3,2), and ( 1,2). (h) 9(3,y] = :3; on the disk :52 + y? C 4 (c) h{.1:,y) = 1D I 6y :2 y2 on the region where :2 i y