To calculate the monthly periodic interest rate from an annual percentage rate (APR), we need to divide the APR by 12 (the number of months in a year). We can use the following formula:
Monthly periodic interest rate = APR / 12
In this case, the APR is 16.75%, so we can plug it into the formula and simplify:
Monthly periodic interest rate = 16.75% / 12
Monthly periodic interest rate = 1.395833...%
Rounding to the nearest hundredth of a percent, we get:
Monthly periodic interest rate = 1.40%
Therefore, the monthly periodic interest rate for the primary credit card holder is 1.40%.