Increasing Discount Formula for Ordering Larger Prints

Hello, my name is Alec and I work for a sign shop called The Banner Factory. I'm a graphic designer and am more creative than I am mathematical so I'm kind of stuck here.

I'm trying to make us a price sheet that will add a discount for increasingly larger-sized orders. We want to start at $10 a square foot and increase to $5 once we get to 25 square feet or more. For example: 1 square foot costs $10, and 25 square feet will cost $125.

I need a formula to create all the prices in between those amounts, then after 25 square feet all items are $5 a square foot.

Can anyone help me with a formula for this? I'd greatly appreciate it.

Thank you.

Hi, I have a same problem with prints calculation. In our case we use range of squere meter for each price. Expl.: 0-1m2 costs $50, 1-2,9m2 - $40, 3-4,9m2 - $35, 5-9,9m2 - $35, and 10+m2 costs $25. How to do it with out make huge data range table with all values, 0,1... incl. I tried IFS, but did not work. thank you, Jiri