Convert Nested Loop to lapply

I am using two loops. In the second loop, I am incrementing value by 1 and then applying filter based on that and converting it to data.matrix so that matrix multiplication can be done in later steps. Is there any way to make it efficient using lapply, expand.grid or any other method?

xx <- structure(list(Ars_0 = c(1308.56, 5728.84, 2177.82), Ars_1 = c(0, 0, 0), 
                    Ars_2 = c(0, 0, 0), age = c(13, 31, 43), region = c('A','A','B')), 
               row.names = c(NA, -3L), 
               class = "data.frame")


mx_long2 = read.table(header = T, text = '
                      Arrears   Ars_0   Ars_1   Ars_2   Seasoning   Region
                      Ars_0 0.985   0.0148  0.0002  mths:36-47  A
                      Ars_1 0.3816  0.286   0.3317  mths:36-47  A
                      Ars_2 0.2959  0.0057  0.2524  mths:36-47  A
                      Ars_0 0.9822  0.0176  0.0002  mths:24-35  A
                      Ars_1 0.389   0.2753  0.3347  mths:24-35  A
                      Ars_2 0.3026  0.0334  0.2399  mths:24-35  A
                      Ars_0 0.9753  0.0243  0.0004  mths:12-23  A
                      Ars_1 0.4002  0.2592  0.3394  mths:12-23  A
                      Ars_2 0.3032  0.0208  0.2387  mths:12-23  A
                      Ars_0 0.8865  0.01332 0.00018 mths:36-47  B
                      Ars_1 0.34344 0.2574  0.29853 mths:36-47  B
                      Ars_2 0.26631 0.00513 0.22716 mths:36-47  B
                      Ars_0 0.88398 0.01584 0.00018 mths:24-35  B
                      Ars_1 0.3501  0.24777 0.30123 mths:24-35  B
                      Ars_2 0.27234 0.03006 0.21591 mths:24-35  B
                      Ars_0 0.87777 0.02187 0.00036 mths:12-23  B
                      Ars_1 0.36018 0.23328 0.30546 mths:12-23  B
                      Ars_2 0.27288 0.01872 0.21483 mths:12-23  B
                      ')


mx_long2 = mx_long2 %>% mutate(minage = as.numeric(substr(as.character(Seasoning), 6,7)),
                               maxage = as.numeric(substr(as.character(Seasoning), 9,10)))


x <- xx %>% select(starts_with('Ars')) %>% data.matrix()

l <- list()
p <- 1

for (i in 1:nrow(x)) {
  for (j in 1:3) {
    Bx = filter(mx_long2, (j + xx[i, 'age']) >= minage, (j + xx[i, 'age']) <= maxage,
                Region == xx[i, 'region']) %>%
      select(starts_with('Ars_')) %>% data.matrix()

    # Matrix Multiplication
    x <-  x %*% Bx
    l[[p]] <- x
    p = p + 1
  }
  }

l