Your goal is to solve the given simple programming exercise. You have been contracted by a local antique store to design an algorithm finding out the total purchases and sales tax. According to the store owner, the user will require to see the subtotal, the sales tax amount and the total purchase amount. A customer is purchasing four items from the antique store. Design an algorithm where the user will enter the price of each of four items. The algorithm will find out the subtotal, the sales tax and the total purchase amount. Suppose that the sales tax is 7%.
Be sure to think regarding the logic and design first (IPO chart, flowchart, and pseudocode). Display all output by using currency formatting.
Advanced (optional): Use a constant for the 7% sales tax.
Complete the given steps:
a) Variable list
b) IPO chart