Create an interactive calculator entirely in bash shell script (Linux programming). This calculator program should have the following features:
- Entry of an expression acceptable to expr
- Accept "q", "quit", or "exit" to exit the scrip
- Accept "h" or "help" and print a short description of feature

The output of the program should look like this: (input is in bold)

Enter an expression: 7
Expr: 7 Answer: 7
Enter an expression: 7+3
Expr: 7+3 Answer: 10
Enter an expression: 2**8
Expr: 2**8 Answer: 256
Enter an expression: foo=9
Expr: foo=9 Answer: 9
Enter an expression: bar=10*foo
Expr: bar=10*foo Answer: 90
Enter an expression: bar
Expr: bar Answer: 90
Enter an expression: help
Welcome to mycal...descriptions...
Enter an expression: foo*bar
Expr: foo*bar Answer: 810
Enter an expression: quit
Existing...