Problem 11 For each of the following sets: A=U[²²₁] n+ n>1 B = {(1₁, 12, 13) ¹ € R³: max{|11|, |12|, |T3|} ≤ 1}, C = {(x₁, x₂)¹ € R² :

0 ≤ x₁ < x₂}, D = {(x₁, 12, 13) € R³ : |1₁| + |1₂|+|T3| = 1, I1, I2, I3 ≥ 0}, n answer the following (a) Is the set closed, open, or neither? (b) Describe the interior and the closure of the set. (c) Is the set bounded and if so, provide a bound. "