Answer: 17.84
To calculate the effective interest rate you'll need the following formula.
(1+ APR / n ) ^n -1 *100.
APR has to be expressed as a decimal, so 0.1642.
n is the period. as it is daily, n=365.
1+(0.1642/365) to the power of 365. will give you 1.1784
Minus 1, and times by 100 to get it as a percentage = 17.84%