Answer:
189.15cy
Step-by-step explanation:
To understand this problem we need to understand as well the form.
It is clear that there is four wall, two short and two long.
The two long are
![\rightarrow 120ft5in+2(10ft)](https://img.qammunity.org/2020/formulas/engineering/college/y2al86eku4eb5lflem359g9ije5ib9lmhc.png)
The two long are
![\rightarrow 122ft1in=122.08ft](https://img.qammunity.org/2020/formulas/engineering/college/5cdk8nl7rn9ccp764fb74a2nieyaulwaxx.png)
The two shors are
![\rightarrow 86ft4.5in = 86.375ft](https://img.qammunity.org/2020/formulas/engineering/college/wa1jcg237b817obh4nmbv8tnv6qdfgswb4.png)
The height and the thickness are 14ft and 0.83ft respectively.
So we only calculate the Quantity of concrete,
![Q_c = [(2*122.08)+(2*86-375)]*14*0.833\\Q_c=4864.02ft^3](https://img.qammunity.org/2020/formulas/engineering/college/daow8qyg1tkev2d3ku8dnh1384p99s43ru.png)
That in cubic yards is equal to
![180.15 (1cy=27ft^3)](https://img.qammunity.org/2020/formulas/engineering/college/wowf1p7lv9zxz1ov2m9ly5o7nju5wqmv94.png)
Hence, we need order 5% plus that represent with the quantity
![Q_(ordered)=1.05*180.15=189.15cy](https://img.qammunity.org/2020/formulas/engineering/college/ichul7wp8wtfl9alkarc1agzhif1frpl60.png)