0 it is at ocean level so elevation is zero
You have the following function:

Derivate implictly the previous expression, as follow:

Where you have used that:

Then, the implicit derivative of the given expression is:

Next, solve for y' as follow:

sinR = 
noting that the sin ratio = 
opposite to ∠P is QR and hypotenuse is PQ ( opposite right angle )
Answer:
3(3a + 4)
Step-by-step explanation:
Just multiple the different answers and find which one is equal to 9a + 12
Distributive property, since 3(2x) you distribute and get 6x