Answer:
648. if you were meaning 36 x 18
but if you meant 36/18 then it is 2
The total area of the blades is the area of a triangle multiplied by 4.
We have then:

Where,
b: base of the blades
h: height of the blades
Substituting values we have:

Doing the calculation we have that the area of the blades is given by:

Answer:
The total area of the blades is:

For complex number, the magnitude is pretty straight forward:
sqrt(6^2 + 2^2) = sqrt(40)
For any a + bi, the magnitude will be sqrt(a^2 + b^2)