Identify the given coordinates and Earth's radius.

Step 1: Identify the given coordinates and Earth's radius.
Point P($\phi_P = 40^\circ N, \lambda_P = 45^\circ W$)
Point Q($\phi_Q = 40^\circ N, \lambda_Q = 135^\circ E$)
Radius of Earth ($R$) = 6370 km (from previous problem context).
$\pi = \frac{22}{7}$ (from previous problem context).

Step 2: Calculate the difference in longitude ($\Delta\lambda$).
Since the longitudes are in different hemispheres (West and East), add them:

$$$$