Nested IF Statement

I'm having great difficulty with my cell E40 formula.

(The formula in cell E38 works perfectly).

I am trying to prevent a negative number from popping up in E40.
A negative amount always pops up if the case threshold of 50 (in cell L1) is not met.
I only want the positive number to appear.


I have tried to insert the usual "greater than and less than" symbols in the formula and cannot seem to make the formula work.
And I have handwritten out the formula and still cannot get it to work.