Problem 1: Write a Python program that counts up the number of vowels contained in a string s. Assume that the string s has been already declared and initialized. Valid vowels are: 'a', 'e'. 'i', 'b' and 'u' (both in capital and lower case letters). For example, if the strings = 'azcbobobegghakl' your program should print: Number of vowels: 5. Problem 2: Write a Python program that requests from the user to enter a string s and then a substring ss. The program will then have to count the number of occurrences of ss in s. For example if the user enters s = 'azcbobobegghakl' and ss = 'bob', then the program should print: Number of times bob occurs is: 2. Problem 3: Write a Python program that requests from the user to enter a string s and then identifies and prints to the screen the longest substring whose characters occur in alphabetical order. For example, if s = 'azcbobobegghakl', then your program should print: Longest substring in alphabetical order is: beggh. In case ties occur, print the first substring. For example, ifs = 'abcbcd', then your program should print: Longest substring in alphabetical order is: abc