Break even yield analys incorporating currency effect?

Question 9D- schweser test 2011 - vol 1- morning test 3 rx = 4.55% => yield for bond X cx = 3.05% => cash rate for currency X ry = 7.05% => yield for bond Y cy = 5.65% => cash rate for currency y Yield advantage of bond X is [(4.55%-7.05%)+(5.65%-3.05%)]=0.1% incorporating currency effect. Question 15.3 - schweser 2011 - vol 2 - afternoon test 2 yield on Nakhon Metal bond (denominated in Baht) = 5.2% cash rate in Baht = 2.5% yield on Powhatan bond (denominated in US dollar) = 4.5% cash rate in US = 6.5% When performing break even yield analysis, they don’t account for currency effect Yield advantage of Nakhon Metal bond = (5.2% - 4.5%). Could you explain that?