Answer
$\theta\approx 84^{\circ}$
Work Step by Step
From the previous part it follows:
$$\cos(\theta)=\frac{r_2^{4}}{r_1^{4}}$$
$$\cos(\theta)=\frac{(0.8)^{4}}{1.4^{4}}$$
$$\cos(\theta)=\frac{256}{2401}$$
$$\theta=\arccos\left(\frac{256}{2401}\right) \approx 84^{\circ}$$
