Answer:
Part a. The cost per unit decreasing by 0.00001 for production levels above 12,000.
Part b. The function for the domain over [12000, 38000] is
.
Part c. The cost per unit at the production level of 19,000 is 0.78.
Step-by-step explanation:
Part a.
From the given graph it is clear that the graph passes through the points (12000,0.85) and (38000,0.59).
If a line passes through two points then the slope of the line is
![m=(y_2-y_1)/(x_2-x_1)](https://img.qammunity.org/2020/formulas/mathematics/high-school/pj0y5tg37a7a9ase0auiwe687ez8iaw2vl.png)
The rate of change in cost per unit for production levels above 12,000 is
![m=(0.59-0.85)/(38000-12000)=-0.00001](https://img.qammunity.org/2020/formulas/mathematics/high-school/8yozom9l3gnzpnwna7ipdefbh3oj170zg7.png)
Here negative sign represents the decreasing rate. It means the cost per unit decreasing by 0.00001 for production levels above 12,000.
Part b.
The point slope form of a linear function is
![(y-y_1)=m(x-x_1)](https://img.qammunity.org/2020/formulas/mathematics/high-school/20o4meve23kz29ft9ldq16hk9naufgor7m.png)
Where, m is slope.
The slope of the line over [12000, 38000] is -0.00001 and the point is (12000,0.85). So, the function for the domain over [12000, 38000] is
![(y-0.85)=-0.00001(x-12000)](https://img.qammunity.org/2020/formulas/mathematics/high-school/h9zgsm1th0psngpt5txy3c269g2i1vr91h.png)
![(y-0.85)=-0.00001x+0.012](https://img.qammunity.org/2020/formulas/mathematics/high-school/svumukaxdtz3l7c7u787kytxzkto6471fy.png)
Add 0.85 on both the sides.
![y=-0.00001x+0.12+0.85](https://img.qammunity.org/2020/formulas/mathematics/high-school/nm7p8lyoyo0a3vd9sztjmkc5qk3xvp22w7.png)
![y=-0.00001x+0.97](https://img.qammunity.org/2020/formulas/mathematics/high-school/tcyk05zc53msy8sjkelr47jrx1ir6qkzdq.png)
The function for the domain over [12000, 38000] is y=-0.00001x+0.97.
Part c.
Substitute x=19000 in the above equation, to find the cost per unit at the production level of 19,000.
![y=-0.00001(19000)+0.97=0.78](https://img.qammunity.org/2020/formulas/mathematics/high-school/cbs66qqjgjbyrpfn3o7oxnxbeha3uj93al.png)
Therefore the cost per unit at the production level of 19,000 is 0.78.