First of all you need to be working with everything in the same units, so either convert ft to m or vice versa. 1 ft is 0.3048 meters, so 4.3 ft * 0.3048 m/ft = 1.31064 m
The scale is the size of the model divided by the size of the real thing. If 1 cm in a map represents 100 m in real life, then considering 100 m are 10,000 cm, the scale would be 1:10,000
In this problem it's the same, you need to find the proportion between the model and the building, which would be 1.31064:525. Or if you divide by the smallest number, 1:400.57
If you work with feet instead of meters, 525 m = 1772.44094 m. So the scale would be 4.3:1772.44094, which if you divide by 4.3 is 1:412.2
