1. Convert an infix expression into postfix using stack.

Infix expression: a + b * c + (d + e * f) + g + h * i * j + k

Identify each step and show the complete stack and the output string on each steps.

2. Evaluate the following postfix expression using stack.

Postfix expression: 20 30 10 * + 20 15 5 * * + 40 5 * +

Identify each step and clearly show the stack with contents for that step.

Please use A spreadsheet or excel file to show the steps. It must be readable and formatted correctly. Thank You :)