[tex]P=ab\\\\6\sqrt{15}=2\sqrt{5}b\\2\sqrt{5}b=6\sqrt{15}\,|\cdot\sqrt{5}\\2\cdot5b=6\sqrt{25\cdot3}\\10b=6\cdot5\sqrt{3}\\10b=30\sqrt{3}\,|\div10\\b=3\sqrt{3}\,[j]\\\\O=2a+2b\\\\O=2\cdot2\sqrt{5}+2\cdot3\sqrt{3}\\\boxed{O=4\sqrt{5}+6\sqrt{3}\,[j]}[/tex]
