The S.C. test on a 1-phase transformer, with the primary winding short-circuited and 30 V applied to the secondary gave a wattmeter reading of 60 W and secondary current of 10 A. II the normal applied primary voltage is 200 V, the transformation ratio 1:2 and the full-load secondary current 10 A, calculate the secondary p.d. at full-load current for (a) unity power factor (b) power factor 0.8 lagging.