We have this formula APR = (Periodic Rate) × (Number of Periods) to get the APR and since it's annual, the number of periods is 12. The question asked about the periodic rate for the first 4 months so relatively, 15.6 is not included in our solution.
We then substitute the known values to the equation to get
4.8 = (Periodic Rate) × (12)
Periodic Rate then is 0.4 which the answer is letter A: 0.4%.