A current of 5.0 A flows for 4.0 h through an electrolytic cell containing a molten slat of metal M. This result in deposition of 0.25 mol of the metal M at the cathode. The oxidation state of M in the molten salt is `+x`. The value of 'x' is (1 Faraday = 96000 C `mol^(-1)`) 3