What would the rating of this transformer be if it were

Question

A 20-kVA 20,000/480-V 60-Hz distribution transformer is tested with the following results:

Open circuit test                                      Short circuit test

(Measured by secondary side)            (Measured by primary side)

VOC = 480 V                                          VSC = 1130 V
IOC = 1.51 A                                          ISC = 1.00 A
VOC = 271 W                                         PSC = 260 W

(a) Find the per-unit equivalent circuit for this transformer at 60 Hz.

(b) What would the rating of this transformer be if it were operated on a 50-Hz power system?

(c) Sketch the equivalent circuit of this transformer referred to the primary side if it is operating at 50 Hz.