I want to plot the Bayes decision boundary for a data that I generated, having 2 predictors and 3 classes and having the same covariance matrix for each class. Can anyone help me with that?

Here is the data I have:

set.seed(123)

x1 = mvrnorm(50, mu = c(0, 0), Sigma = matrix(c(1, 0, 0, 3), 2))

x2 = mvrnorm(50, mu = c(3, 3), Sigma = matrix(c(1, 0, 0, 3), 2))

x3 = mvrnorm(50, mu = c(1, 6), Sigma = matrix(c(1, 0, 0, 3), 2))