In order to calculate the impulse, you need to find out the area of the triangle,
Area of triangle = 1/2 * b * h
Here, b = time = 40
h = force = 100
Substitute their values,
A = 1/2 * 40 * 100
A = 1/2 * 400
A = 200 N.s
In short, Impulse and your answer would be 200 Newton-second
Hope this helps!
