Two points $A$ and $B$ on the surface of the Earth are at the same longitude and $60.0^{\circ}$ apart in latitude and $60.0^{\circ}$ apart in latitude as shown in Figure PI6.4. Suppose an earthquake at point $A$ creates a P waveling straight through the body of the Earth at a constant speed of 7.80 $\mathrm{km} / \mathrm{s}$ . The earthquake also radiates a Rayleigh wave that travels at 4.50 $\mathrm{km} / \mathrm{s}$ . In addition to $\mathrm{P}$ and $\mathrm{S}$ waves, Rayleigh waves are a third type of seismic wave that travels along the surface of the Earth rather than through the bulk of the Earth. (a) Which of these two seismic waves arrives at $B$ first? (b) What is the time difference between the arrivals of these two waves at $B ?$