Given the premise set ={p,q,r,s} and =(pq)r, what is the unweighted upper bound of the uncertainty of

Given the premise set Γ={p,q,r,s} and ϕ=(p∨q)∧r, what is the unweighted upper bound of the uncertainty of the conclusion ϕ, if the probability of each element of Γ is 0.9?