Answer
a) Beth will reach the San Francisco first.
b) Beth have to wait for $20 \space minutes $ fo Alan.
Work Step by Step
a) Time taken by Alan to reach San Francisco $ = \frac{400 mi}{50 mph} = 8 \space hours$
Thus Alan will reach San Francisco at $(8:00 \space a.m + 8 hours) = 4:00 \space p.m$
Time taken by Beth to reach San Francisco $ = \frac{400 mi}{60 mph} = 6\frac{2}{3} \space hours = 6 hours \space and \space 40 mins$
Thus Beth will reach San Francisco at $(9:00 a.m + 6 \space hours\space 40 mins) = 3:40 p.m$
Hence Beth will reach the San Francisco first.
b) Since Beth will reach at $3:40 \space p.m$ and Alan at $4:00 pm$ .
So Beth have to wait for $20 \space minutes $ fo Alan.
