Instruct: Which Men's 50 has a Senior Mixed of n/A, and a Men's Open of gold coast sharks def sydney mets, and a Men's 30 of sydney mets def sydney scorpions, and a Women's u20 of southern suns def brisbane city cobras?
Output: SELECT Men's 50 FROM table WHERE Senior Mixed = n/a AND Men's Open = gold coast sharks def sydney mets AND Men's 30 = sydney mets def sydney scorpions AND Women's u20 = southern suns def brisbane city cobras