Write one-line commands that perform the followings in a Linux environment.

1. List all files in the sub-directories of /etc that end with .conf . For example, it should list /etc/cups/cupsd.conf, but should not list /etc/host.conf .

2. Create a set of directories in the current directory named based on three-letter month and four-digit year between 2015 and 2018. Directories should be named Jan2015, Feb2015, ..., Nov2018, Dec2018.

3.Calculate and show the result for a simple multiplication (such as 2*3) provided in a file named multiply.txt. You can only use cat and echo commands for performing this.