From the information given,
The equation representing the relationship between the size of the blade (b) in inches and speed (miles/hour) is given as
Speed = 50-2b
Also, the required drone must travel faster than 37 miles/hour.
For the small blade, b = 4 inches
speed = 50 - 2 * 4 = 50 - 8
speed = 42 miles/hour
For the medium blade, b = 6 inches
speed = 50 - 2 * 6 = 50 - 12
speed = 38 miles per hour
For the large blade, b = 8
speed = 50 - 2 * 8 = 50 - 16
speed = 34 miles per hour
Since the speed of the drone with small blade is greater than 37 miles per hour and it is the greatest among the three drones,
The speed of the drone will be 42 miles per hour