1) Considering that the slant height of those pyramids is 4 and 6, we can find the scale factor by dividing their slant heights:

So we can state that the bigger pyramid is larger than the 1st pyramid by a scale factor of 1.5.
2) For the Volume of the Pyramid, we can write out the formula below:

Since the scale factor is 1.5 Then we can state that

the Volume of the smaller one is by similarity 1.5 or 3/2 times smaller than the larger one.
3) Hence, the answers are:
1.k=1.5
2. 32 m³