For this case we have the following vectors:

The dot product of two vectors is a scalar.
The point product consists of multiplying component by component and then adding the result of the multiplication of each component.
For the product point of the vectors a and b we have:
Answer:
The product point of the vectors a and b is:
Answer:
The ratio of their surface areas is 
Step-by-step explanation:
we know that
If two figures are similar, then the ratio of its corresponding sides is equal and this ratio is called the scale factor
In this problem the scale factor is equal to the ratio 
and
Remember that
If two figures are similar, then the ratio of its surface areas is equal to the scale factor squared
therefore
In this problem the ratio of their surface areas is 
16.4
20.5/5=4.1
4.1*4=16.4
............