2. (4 marks) Determine whether the following limits exist. If so, determine their value. -2-12 (a) (1 mark) lim(z,y)-(0,0) 72 +y- 1 (b) (1 mark) lim(z,y) (0,0) -ty-1 (c) (2 marks) lim(r.y)-(0,0) VIty Hint: (x - y)2 2 0]