From the question
By the bunkers rule
[tex]I=\text{PRT}[/tex]P = 18,000
R = 17.25% = 0.1725
For the time
Since the year is a leap year then
February has 29 days
Hence
From Feb.4 to Apr 21 implies
The number of days left in Feb. = 25
Number of days in March = 31
Number of days for April = 21
Therefore, Total number of days = 25 + 31 + 21 = 77
By Bankers rule, total days for the year will be 360
Hence the interest is
[tex]\begin{gathered} I=18000\times0.1725\times\frac{77}{360} \\ I=18000\times0.1725\times0.2139 \\ I=664.16 \end{gathered}[/tex]Therefore, the interest is 664.16
