8. Write a simple script named 'surface_of a_rectangle.sh' in which you assign two integer values to two variables. The script then calculates the surface of a rectangle which has these proportions. It should be paired with comments and generate elegant output. 9. Run command 'cat surface of a_rectangle.sh' to display the content of your script 10.Make your script executable and run your script 11.Change the value of the two variables in your script then run your script again