String Manipulation

Question

Hello, how would i go about achieving the following requests. I am new to this.  Can i achieve all the results from once class or calling different classes.  Im'm not sure if I have asked the questions correclty. Please help.  Here is want i need to accomplish.

Write a program "StringManipulation.cs" in C# which accepts
two strings as command line arguments. The program should do the following:

i)  print and display the total number of occurrences of the character „a? or
„A? present in both the strings
ii)  replace every occurrence of „a? or „A? with @
iii)  convert both the strings to upper case
iv)  concatenate the two strings and display the result

Thanks