To calculate the APR, we first calculate the monthly rate and then the APR (Annual percentage rate)
Monthly rate is calculated by using RATE function in excel as in =RATE(NPER,PMT,PV) where
NPER = number of period in months = 48
PMT = Monthly payment = 960
PV = Loan value = 38400
Monthly rate = RATE(48,960,-38400) = 0.77015%
APR = Monthly rate * 12
APR = 0.77015%*12
APR = 9.24% (Rounded to 2 decimals)