The rate at which a cell absorbs an external signalling molecule xx through the cell membrane can be described by the absorption function

A(x)=5x/e^2x

1. Calculate A(x) and find a value for x such that the absorption function has a horizontal tangent line.
2. What is the absorption rate at this value of x ?
3. Find this tangent line.
4. Would you expect this absorption function to be the same for all cell types and for all signalling molecules x?