Ubuntu – CakePHP error: cake_core_ cache was unable to write ‘cake_dev_en-us’ on Ubuntu 14.04

When I run my CakePHP application on localhost Ubuntu 14.04 (LAMP) I get this error:

Warning: _cake_core_ cache was unable to write 'cake_dev_en-us' to
File cache in /var/www/html/tmc/lib/Cake/Cache/Cache.php on line 328

Warning: /var/www/html/tmc/app/tmp/cache/persistent/ is not writable
in /var/www/html/tmc/lib/Cake/Cache/Engine/FileEngine.php on line 385

Fatal error: Uncaught exception 'CacheException' with message 'Cache
engine "_cake_core_" is not properly configured. Ensure required
extensions are installed, and credentials/permissions are correct' in
/var/www/html/tmc/lib/Cake/Cache/Cache.php:186 Stack trace: #0
/var/www/html/tmc/lib/Cake/Cache/Cache.php(151):
Cache::_buildEngine('_cake_core_') #1
/var/www/html/tmc/app/Config/core.php(386):
Cache::config('_cake_core_', Array) #2
/var/www/html/tmc/lib/Cake/Core/Configure.php(72):
include('/var/www/html/t…') #3
/var/www/html/tmc/lib/Cake/bootstrap.php(431):
Configure::bootstrap(true) #4
/var/www/html/tmc/app/webroot/index.php(97):
include('/var/www/html/t…') #5 {main} thrown in
/var/www/html/tmc/lib/Cake/Cache/Cache.php on line 186

I am not sure where is the issue. I tried sudo chmod 775 /var/www/html/tmc/lib/Cake/Cache/Engine/FileEngine.php command but it didn't fix the issue.