The answer is $89.28.
Let's use the proportion for this:
If 1400 ft² costs $125,000, 1 ft² will cost x:
1400 ft² : $125,000 = 1 ft² : x
Now, crossing the products:
x · 1400 ft² = $125,000 · 1 ft²
x · 1400 = $125,000
x = $125,000 ÷ 1400
x = $89.28
Therefore, 1 square foot costs $89.28.