M is always positive is not true.
Hope this helps!
Answer:
The volume of the pyramid is 
Step-by-step explanation:
we know that
The volume of the triangular pyramid is equal to

where
B is the area of the triangular base
H is the height of the pyramid
step 1
Find the area of the base B

we have


substitute

step 2
Find the volume
we have


substitute


We must find the difference between prices. $2.65 - $2.50 = $0.15. Now we need to calculate what percent $0.15 is of $2.65. It is 5.7%! The price decreased, so it is a 5.7% decrease!