Don't see "tree" package in my installation list

[lqian]

Hello,
Recently I updated my R and Rstudio and tried to install tree package, but don't see it.
I am looking for help. The error message is given below.

(as ‘lib’ is unspecified)
Warning in install.packages :
  package ‘tree’ is not available (for R version 3.5.3)

I have tried on two computers via both R console using install.packages("tree") and Rstudio package install, neither of them found tree packages on neither of computers. Your help will be very much appreciated.
Thanks,
Lianfen

[andresrcs]

The tree package depends on R (≥ 3.6.0) and apparently you are using 3.5.3 version.
You would have to update R in order to install tree package.

[lqian]

Thanks and I figured it out too.