First compute the cash price per $100 face value:

$$Y = 100 - 5.00\cdot\frac{90}{360} = 98.75$$

Then compute the effective yield:

$$\text{True Yield} = \frac{100 - 98.75}{98.75}\cdot\frac{360}{90}$$ $$= 5.06329\%$$

This is already on an ACT/360 basis with discrete quarterly compounding, so no conversion is needed. The correct answer is 5.06%.