Which graph shows the lowest cost per square foot for a new home?

We are given following coordinates in given graphs (1000,12000), (1500, 16000), (500 , 8000) , (2000, 18000).

Let us discribe each given coordinate and cost per square foot area for each coordinate (in each graph).

1st (1000,12000) : represnts 1000 square foot area cost $12000.

Cost per square feet = 12000/1000 = $12.

2nd (1500, 16000) : represnts 1500 square foot area cost $16000.

Cost per square feet = 16000/1500 = $10.67.

3rd (500 , 8000)  : represnts 500 square foot area cost $8000.

Cost per square feet = 8000/500 = $16.

4th (2000, 18000) : represnts 2000 square foot area cost $18000.

Cost per square feet = 18000/2000 = $6.

Therefore, 4th graph with (2000, 18000) coordinate shows the lowest cost that is $6 per square foot for a new home.

The graph that has the lowest cost per square foot for a new home is the graph which has the lowest slope.

Hence, we will calculate the slope in each of the graph.

As each of the graph passes through (0,0) and some point (a,b)

Hence, the slope is:

By looking at the figure attached to the answer we could see that the last graph has the smallest slope.