How to include tier's in to a formula ?

example, say I tell you, if you score 1000 points I will pay you in tiers.


You score 1000,

Tier 1 - For the first 150 pts I will pay 150 pts * 25
Tier 2 - For the second 400 pts I will pay 400 pts* 30
Tier 3 - For the remaining pts I will pay 450 pts*15



My question is, regardless if 1000 points or less.. what forumla can I use to to include the tiers in my calculation?

Excel sample attached to this post. Thank you

edit to post: If it makes it easier I am ok even having to have 3 seperate formuals (per tier) , I can just add the the values to make my total. Although 1 formula would be nice.