I'm following Tools Used in 6.828 to configure.$ sudo tar xjf binutils-2.21.1.tar.bz2generate folder binutils-2.21.1$ cd binutils-2.21.1cd: permission denied: binutils-2.21.1$ sudo cd binutils-2.21.1sudo: cd: command not foundPermissions of this folder's Properties show me I have Read & Write access.How could I go into this folder (and build it)?$ ls -ldrwxrwx--- 18  500  500     4096 Aug 24  2011 binutils-2.21.1-rw-r--r--  1 root root 18997755 Aug 26  2011 binutils-2.21.1.tar.bz2drwxr-xr-x 21  500  500     4096 Apr 26 20:40 gcc-4.6.1-rw-r--r--  1 root root 30117877 Jun 27  2011 gcc-core-4.6.1.tar.bz2drwxr-xr-x 15 1001 root     4096 Apr 26 21:55 gmp-5.0.2-rw-r--r--  1 root root  2024576 Apr 26 21:39 gmp-5.0.2.tar.bz2 drwxr-xr-x  6 rahn rahn     4096 Apr 26 22:00 mpc-0.9-rw-r--r--  1 root root   565953 Jan 19 05:11 mpc-0.9.tar.gz drwxr-xr-x  9 rahn rahn     4096 Apr 26 21:57 mpfr-3.1.4-rw-r--r--  1 root root  1279284 Mar  6 21:43 mpfr-3.1.4.tar.bz2Debian 8.4, zsh
cd: permission denied: binutils-2.21.1
debian;permissions;cd command