Step 1 :Convert the annual interest rate to a monthly rate: \(\frac{r}{n} = \frac{55\%}{12} = 0.0458333\) or 4.58333%
Step 2 :Substitute the given values into the formula: \(M = 18000 \times \left[\frac{0.0458333}{1 - (1 + 0.0458333)^{-12 \times 3}}\right]\)
Step 3 :Calculate the denominator: \(1 + \frac{r}{n} = 1 + 0.0458333 = 1.0458333\)
Step 4 :Calculate the power: \((1 + \frac{r}{n})^{-n \times t} = (1.0458333)^{-36} = 0.0301539\)
Step 5 :Subtract from 1: \(1 - (1 + \frac{r}{n})^{-n \times t} = 1 - 0.0301539 = 0.969846\)
Step 6 :Calculate the numerator: \(P \times \frac{r}{n} = 18000 \times 0.0458333 = 825\)
Step 7 :Divide the numerator by the denominator to find the monthly payment: \(M = \frac{825}{0.969846} = 850.37\)
Step 8 :\(\boxed{M = 850.37}\)