ANSWER :
0.04 minute
EXPLANATION :
We have two scenarios, one is going up then taking a turn.
The other is one is by directly cutting the corner.
The total distance when going up then taking a turn is 36 ft + 16 ft = 52 ft
The distance when cutting the corner is 39.4 ft
Recall the distance formula :

where d = distance
v = speed
t = time
From the problem, the speed is 4 mph.
Let's convert the speed into feet per minute.
Note that 1 mile = 5280 feet
1 hour = 60 minutes
The conversion will be :

So the speed is 352 ft per min
Use the distance formula above to solve the time needed in each scenario.

Get the difference to solve how much time can you save.
0.15 min - 0.11 min = 0.04 minute