4. A company's income and expenditure from 2013 to 2017 are shown in Table 1.
According to the data in the table, the regression line equation is
$$
\hat{y}=0.8 x+\hat{a} \text {, }
$$

Based on this estimate, the expenditure of the company in 2018 when the income is 7 billion yuan is $(\quad)$ billion yuan.
(A) 4.5
(B) 4.4
(C) 4.3
(D) 4.2
4. B.
$$
\begin{array}{l}
\text { Given } \frac{0.2+1.5+2.0+2.5+3.8}{5} \\
=0.8 \times \frac{2.2+2.6+4.0+5.3+5.9}{5}+\hat{a} \\
\Rightarrow \hat{a}=-1.2 .
\end{array}
$$

When $x=7$, $y=0.8 \times 7-1.2=4.4$.