Question 17:
Write a Python program to accept cost price and selling price, then print whether there is profit, loss, or no gain.

Answer:
def main(cost_price: float, selling_price: float) -> None:
    if selling_price > cost_price:
        print(f"Profit: {selling_price - cost_price}")
    elif selling_price < cost_price:
        print(f"Loss: {cost_price - selling_price}")
    else:
        print("No gain, no loss.")

if __name__ == '__main__':
    main(100.0, 120.0)
    main(150.0, 130.0)
    main(200.0, 200.0)

Output:
Profit: 20.0
Loss: 20.0
No gain, no loss.