we can use the formula for average speed when dealing with different speeds in two segments:
average speed = 2 * (speed1 * speed2) / (speed1 + speed2)
In this case,
speed1 = 40 mph (driving home)
speed2 = 60 mph (driving back to work)
average speed = 2 * (40 * 60) / (40 + 60)
average speed = 2 * (2400) / (100)
average speed = 4800 / 100
average speed = 48 mph
So, Janet's average speed for the entire trip is 48 mph (Option A).