Calculate the volume of both the prism and the cubes:
Prism:
Volume = 20 x 2 x 3.25 = 130 cubic inches.
Volume of cube:
Volume = S^3 = 1/4^3 = 1/64 ( 0.015625)
Divide the area of the prism by the area of the cube:
130 / 1/64 = 130 * 64 = 8,320
It would take 8,320 cubes to fill the prism.
We know, Time = distance / speed
t = 0.0568182 / 50 [ 300 Feet = 0.0568182 miles ]
t = 0.001136 * 3600 s
t = 4.09 sec
In short, Your Answer would be 4.09 Seconds
Hope this helps!