Design a solution and write its C++ code by using switch-case statements. It takes an integer argument and checks if it is a positive integer. In case of a zero or negative input it displays an error message. In case of a positive input it displays following output:

A if the input is between 1 and 30 (1 and 5 included)

B if the input is between 31 and 70 (3 and 7 included)

C if the input is between 71 and 100 (71 included)

D if the input is between 100 and 150 (100 and 150 included)

F if the input is greater than 150.

Keep your code commented and indented for ease of reading. Paste your commented codes in the solution and also add a clear screen shot of outcome in your solution.