I am new to the application of Rstudio and have been facing issues regarding the installation of certain package. How am I supposed to rectify this issue ? –

Warning in install.packages :
  unable to access index for repository http://cran.rstudio.com/bin/windows/contrib/3.6:
  cannot open URL 'http://cran.rstudio.com/bin/windows/contrib/3.6/PACKAGES'
Packages which are only available in source form, and may need compilation of C/C++/Fortran: ‘xts’ ‘zoo’
  ‘TTR’
  These will not be installed
> install.packages("lattice")
Warning in install.packages :
  package ‘lattice’ is not available (for R version 3.6.1)
Warning in install.packages :
  unable to access index for repository http://cran.rstudio.com/bin/windows/contrib/3.6:
  cannot open URL 'http://cran.rstudio.com/bin/windows/contrib/3.6/PACKAGES'
> install.packages("zoo")
Warning in install.packages :
  dependency ‘lattice’ is not available
Warning in install.packages :
  unable to access index for repository http://cran.rstudio.com/bin/windows/contrib/3.6:
  cannot open URL 'http://cran.rstudio.com/bin/windows/contrib/3.6/PACKAGES'
Package which is only available in source form, and may need compilation of C/C++/Fortran: ‘zoo’
  These will not be installed

I am trying to add packages to start a monte carlo simulation but cant apply the packages necessary for it.