Please write a C program to complete the requirements as below:

• Ask the user to type in a string with a length less than 15 and store it.
• Define one string with the assigned value abcdef, and define another string with the assigned value 123456. Compare these two and print out the bigger one.
• Append the bigger string between abcdef and 123456 to the string the user entered, and figure out the length of it; finally, print out the combined string as well as its length.