A single-phase step-down transformer is rated 15 MVA, 66 kV/11.5 kV. With the 11.5 kV winding short-circuited, rated current flows when the voltage applied to the primary is 5.5 kV. The power input is read as 100 kW. (a) Determine Req1 and Xeqi in ohms referred to the high voltage winding. (b) The open-circuit test with 11.5 kV applied results in a power input of 65 kW and current of 30 A. Compute the values of Ge and Bm siemens referred to the high-voltage winding. Compute the efficiency of the transformer for a load of 10 MW at 0.8 p.f. lagging at rated voltage.