I think the answer is B. because the formula for the volume of a rectangular prism is length times width times height.
For the bigger one:
length = 3
width = 10
height = 6
the big one = 3*10*6
For the smaller one:
length = 3
width = 4
height = 6
the small one = 3*4*6
That equals: 10*3*6 and 4*3*6
length, with, and height order doesn't matter because it's still gonna be the same.
hope this helped☺☺