Between nodes a-b there is only the symbol of an inductor, which does not necessarily means that the model represented by XL is an ideal device, that is, this 'inductor' may contain parasitic elements (let's say, a series resistor) so that the unknown paramter could be the angle between the real and imaginary components, once the magnitude is a known datum, a vector of amplitude 10K. Anyway, it is evident that the attached question has not been well elaborated, leaves room for different interpretations, therefore I would not concern on this, as long as your methematical calculations come out correct for any of these interpretations.