For this case we have by definition that the area of a parallelogram is given by:

Where:
b: It's the base
h: It's the height
According to the data we have:

Substituting in the formula:

The area of the parallelogram is 
Answer:

Yes it is a natural number
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Answer: (a) e ^ -3x (b)e^-3x
Step-by-step explanation:
I suggest the equation is:
d/dx[integral (e^-3t) dt
First we integrate e^-3tdt
Integral(e ^ -3t dt) as shown in attachment and then we differentiate the result as shown in the attachment.
(b) to differentiate the integral let x = t, and substitute into the expression.
Therefore dx = dt
Hence, d/dx[integral (e ^-3x dx)] = e^-3x