a)
[tex]a = 3\sqrt{2} \ cm\\b = \sqrt{2} \ cm\\\\P = a\cdot b\\\\P = 3\sqrt{2}\cdot\sqrt{2}\\\\P = 3\sqrt{2\cdot2}\\\\P = 3\cdot 2\\\\\boxed{P = 6 \ cm^{3}}[/tex]
[tex]Ob = 2a + 2b = 2(a+b)\\\\Ob = 2(3\sqrt{2}+\sqrt{2})\\\\Ob = 2\cdot4\sqrt{2}\\\\\boxed{Ob = 8\sqrt{2} \ cm}[/tex]
b)
[tex]a = \sqrt{12} \ cm = \sqrt{4\cdot3} \ cm = 2\sqrt{3} \ cm\\b = \sqrt{3} \ cm\\\\P = a\cdot b\\\\P = 2\sqrt{3}\cdot\sqrt{3}\\\\P = 2\sqrt{9}\\\\P = 2\cdot3\\\\\boxed{P = 6 \ cm \ ^{2}}[/tex]
[tex]Ob = 2(a+b)\\\\Ob = 2(2\sqrt{3}+\sqrt{3})\\\\Ob = 2\cdot3\sqrt{3}\\\\\boxed{Ob = 6\sqrt{3} \ cm}[/tex]