Write a program, with comments, to do the following:$(28+2=30)$ a$.$Initialize a stringstr$1.$str$1$should contain $5-10$ characters. Printstr$1$ b$.$Ask the user to enter a positive integer between $1$ and $26$ and assign it to a variablen. Printn. Assume the user will enter an integer, but it may not be in the proper range. c$.$Check ifnis in the proper range. Ifnis in the proper range i$.$Create a variablexand assign it the value of thenth letter of the alphabet in lowercase. Printxwith a suitable message. HINT: You can use the built$-$inord$()$andchr$()$functions$.$ ii$.$Find the number of occurrences ofxinstr$1$and print this value with a suitable message. otherwise print a message saying that the user entered an invalid input. d$.$Printstr$1$centered in a field of $20$ characters, with $*$ used as padding.