Answer
The money earned on a sales day
Work Step by Step
The statement indicates that $\mathcal{a, b}$ and $\mathcal{c}$ represent the quantity of products that were sold; While 2, 1.5 and 1 are the prices of each of those products.
If $\vec{A}=\left \langle {\mathcal{a, b, c}} \right \rangle$ and $\vec{P}= \left \langle {2, 1.5,1} \right \rangle$
Then, it's about the relationship between the quantity of products sold ($\vec{A}$) and the cost of each product ($\vec{P}$), so $\vec{A}\cdot\vec{P}$ would be the money earned in a day.
$A\cdot P=(a,b,c)\cdot (2,1.5,1)=2a+1.5b+c$
