Step-by-step explanation:
We are given the unit cost to produce x number of airplanes as follows;
![C(x)=0.5x^2-150x+26777](https://img.qammunity.org/2023/formulas/mathematics/college/e033uy59oii5a5aeebfsrpi8tivipxgbg3.png)
However, to minimize the unit cost, we need to first take the derivative of the cost function and then find its value at zero.
Thuis is shown below;
![C(x)=0.5x^2-150x+26777](https://img.qammunity.org/2023/formulas/mathematics/college/e033uy59oii5a5aeebfsrpi8tivipxgbg3.png)
![(d)/(dx)=2(0.5)x^(2-1)-1(150)x^(1-1)+0](https://img.qammunity.org/2023/formulas/mathematics/college/wgpo8vyc5x4oatxj7mlnv6mgcd7v35p09g.png)
Note that for a derivative, the constant term is always equal to zero. We can now simplify what we have above;
![(d)/(dx)=1x^1-150](https://img.qammunity.org/2023/formulas/mathematics/college/hh3nl4s54uuno9jh4tscpapinpoaz8qqod.png)
![(d)/(dx)=x-150](https://img.qammunity.org/2023/formulas/mathematics/college/5bwzdvely80aa17um5yufxbcq1ilryyhps.png)
We now set this equal to zero and simplify;
![x-150=0](https://img.qammunity.org/2023/formulas/mathematics/college/nwkvxb8352gdvs67g9qk7w5jrul98bj4or.png)
Add 150 to both sides;
![x=150](https://img.qammunity.org/2023/formulas/mathematics/college/h77sb4z490hcg6gqa4vixrsobdlpudvvry.png)
ANSWER:
Therefore, to minimize the unit cost, 150 engines must be made.