Finding the unit

Question

I have the equation:

And the following units:

for time is the day

for the alfa and p is day^(-1)

for S, s(i) and k is u*mol/L

for X is mm^3/L

I have to find the unit for y but I don't know how to do that, I tried by writing the equation only with units but when to simpify it gives me a strange unit.