The #Co^(2+)andPO_4^(3-)# ions will form a precipitate.
Explanation:
So we can leave out the #Cl^(-) andNa^+# ions, as they are only 'spectators', i.e. they will be left unchanged in the solution.
Since #Co# has a charge of +2 and #PO_4# has a charge of -3, we will have to take 3 of the first and 2 of the other to make charges equal (but opposite):