Assume that the expected form of a file name is name. digits. ext. file names conforming to this form are, for example: experiment.34.dat, subjects.241.fig, simulation.0001.log. write a script that will repeatedly prompt the user to enter a file name until they enter a string conforming to the valid file name form. the string is in the valid form if it consists of a name (letters only), followed by a dot, followed by digits only, followed by a second dot, followed by a three-character extension consisting of letters only. the script should inform the user each time they enter an invalid file name, and the user once they have entered a valid file name. here is an example of what executing the script might look like: enter a file name: book. txt