Challenge: Calculating Total Cost with Discounts and Tax

Implement a shopping cart system that calculates the total order cost, applying a discount and sales tax based on predefined conditions.

1. Use map() to get the total price of each product (there is a dedicated method getTotalPrice() in the Product class).
2. Apply reduce() to sum up all product prices.
3. Use a ternary operator to check if the subtotal exceeds the discount threshold (DISCOUNT_THRESHOLD) and calculate the discount. If subtotal is greater than the threshold, apply a 10% discount (DISCOUNT_PERCENTAGE); otherwise, set the discount to 0.0.
4. Determine the discount amount by multiplying subtotal by DISCOUNT_PERCENTAGE.
5. Calculate the pre-tax amount (preTaxAmount) by subtracting discount from subtotal.
6. Compute the sales tax (tax) by multiplying preTaxAmount by the sales tax rate (SALES_TAX).
7. Return the final total, calculated as preTaxAmount + tax.