Here's how to solve the problem step-by-step: Given: Radius of the Earth, $R = 6370$ km. Speed of plane S = 420 knots. Points: P($40^\circ$N, $45^\circ$W) Q($40^\circ$N, $45^\circ$E) T($35^\circ$N, $135^\circ$E) a) Find the distance from P to Q in km. Step 1: Determine the difference in longitude ($\theta$) between P and Q. P is at $45^\circ$W and Q is at $45^\circ$E. Since they are on opposite sides of the Prime Meridian, we add their longitudes. $$ \theta = 45^\circ + 45^\circ = 90^\circ $$ Step 2: Identify the latitude ($\alpha$) for P and Q. Both P and Q are at $40^\circ$N latitude.