Save Money Calc

It is a computer useful by the sale.
Three patterns can be calculated.

[Discount calculation]
･Two discounts of 500 dollars?
･50 dollar off of 300 dollars?

[The same weight]
The amount of money when making it to the same weight is calculated, and it is possible to compare it.
･Which is cheap when it is a commodity of 150 dollars for 100g, a commodity of 200 dollars for 150g, and the same 100g?

[Point]
･How many points can you obtain if it buys for 100 dollars, and the point is reduced by 10%?