One mole of $CoCI_3, YNH_3$ complex compound on complete ionisation in water produce three moles of ions. If one chloride satisfies both primary and secondary valencies of cobalt ion, the value of Y is :

Question

$\begin {array} {1 1} (1)\;3 & \quad (2)\;4 \\ (3)\;5 & \quad (4)\;6 \end {array}$