A warehouse charges its customers $4 per day for every 10 cubic feet of space used for storage. The figure records the storage used by one company over a month. How much will the company have to pay?

Figure 1 is the original figure, while figure 2 is modified, so that a triangle and a rectangle can be easily observed.

The area of triangle and rectangle represents the total number of cubic feet of storage multiply by the number of days of storage usage.

Hence

Total Area = Area of triangle + Area of rectangle

= 30 x 10,000 + ½ 30 x (30,000 - 10,000)

= 300,000 + 300,000

= 600,000

As 10 cubic feet of storage cost $5 for a day, so total amount company have to pay

= (5 x 600,000) / 10 = $300,000