Solution:
To solve this problem, we will use PRT/100.
Where:
1. Converting the number of months into years.
[tex]\bullet \ \ 1 \ \text{year} = 12 \ \text{months}[/tex]
[tex]\bullet \ \ \rightarrow \text{x years = 12x months = 18 months}[/tex]
[tex]\bullet \ \ \rightarrow \frac{12x}{12} = \frac{18}{12}[/tex]
[tex]\bullet \ \ \rightarrow x = 1.5 \ \text{years}[/tex]
2. Using PRT/100:
[tex]\bullet \ \ \rightarrow \dfrac{P \times R \times T}{100}[/tex]
[tex]\bullet \ \ \rightarrow \dfrac{1900 \times 5.9 \times 1.5}{100}[/tex]
[tex]\bullet \ \ \rightarrow19 \times 5.9 \times 1.5}[/tex]
[tex]\bullet \ \ \rightarrow \boxed{\$168.15}[/tex]
Thus, the interest will be [tex]\bold{\$168.15}[/tex].