John and Derek, both calendar$-$year taxpayers, each own a $20\%$ interest in Partnership WXYZ$.$ Elite$18,$ Inc., a corporation whose fiscal year ends on July $30$ of each year, owns a $60\%$ interest in Partnership WXYZ$.$ Partnership WXYZ has not established a business purpose for using a different tax year, nor has it made a fiscal year tax$-$year election. On what date will Partnership WXYZ$\text{'}$s taxable year end?

March $15.$

April $15.$

July $30.$

December $31.$