Question

Suppose fred ethel ricky and lucy have the following demand functions for a public good
Qf= 40-1/2p
Qe= 20-p
Qr= 30-1/2p
Ql= 50-p

The good can be produced at a constant cost of 5 dollars

Calculate the Lindahl Equilibrium


I know that the lindhal is the vertical summation of each price given a quantity but i have no idea how to calculate the EQ