X and Y are two alloys of copper and aluminium prepared by mixing the metals in the ratio 6 : 5 and 5 : 9, respectively. If equal quantities of the alloys are melted to form a third alloy Z, what ratio of copper and aluminium will be in Z?

A

154 : 163

B

165 : 139

C

139 : 154

D

139 : 169