Find P(X+Y>1) probability of density function

Find P(X+Y>1) probability of density function

Yet another PDF question.
I am given the following joint density function,
$$f_{X,Y}(x,y)=\frac{2}{5}\text{ when }0<y<1\text{ and } 0<x<5y$$
And have to calculate the probability that $X+Y>1$
I have drawn a figure which shows the area in question,
The red area is where the PDF equals $\frac{2}{5}$, and the area to the
right of the line $y=x-1$, is where $X+Y>1$

So if I understand correctly, I have to double integrate the PDF to find
the area to the left of the line. But im not having any luck getting the
correct answer.
Thanks in advance :)