A population p(t) satisfies dp/dt = f(p), where f(p) = kp (1-p/a)(1-p/b)

The population lies in the interval 0<=p<=b

k,a,b are positive constants with b>a

Determine all equilibrium points.

For this part f(p)=0 so p=0, p=a, p=b

Then I have to sketch f as a function of p. I know by expanding f(p) that is a cubic equation but I don't have any data about k,a,b except that they are all >0.

I found f'(p) and solved it to be equal to zero to find the stationary points, i found an answer but was a complete mess. I don't know what we are expected to sketch exactly without any further information.

I will appreciate any help. Thanks in advance!