Let
L------> the length of the base of the pyramid
W-----> the width of the base of the pyramid
H-----> the height of the pyramid
V------> Volume of a rectangular pyramid
we know that
V=(1/3)*[L*W]*H
so
the three variables are going to have the same influence on the volume
example
case a)
let's change the variable L (we reduce the variable by half)
L=(1/2)*L
the new volume is equal to
V new=(1/3)*[(L/2)*W]*H-----> V new=(1/2)*V
the new volume is half the original volume
case b)
let's change the variable W (we reduce the variable by half)
W=(1/2)*W
the new volume is equal to
V new=(1/3)*[(W/2)*L]*H-----> V new=(1/2)*V
the new volume is half the original volume
case c)
let's change the variable H (we reduce the variable by half)
H=(1/2)*H
the new volume is equal to
V new=(1/3)*[L*W]*H/2-----> V new=(1/2)*V
the new volume is half the original volume
therefore
the answer is
the three variables have the same influence on the volume