how to obtain system throughput with power graph

this is the graph

this is the equation

and the code i have tried so far

tow=.34
Pa=5:5:15
Ps=10
Pi=[0.3,1,1.6]
N=3
gs=[1.5,2.5,3.5]
yi=[1,2,4]
Pt=((tow*Pa)./(1-tow))
n1=(Pt-sum(Pi(2:N)))*yi(1)
d1=(Ps*gs)+sum(Pi(2:N).*yi(2:N))
a=log2(1+(n1./d1))
res=0
for i=2:N
    n2=Pi(i)*yi(i)
    d2=Ps*gs+sum(Pi(3:N)*yi(3:N))
    fin=log2(1+(n2./d2))
    res=res+fin
end
rsum=a+res
plot(Pa,rsum)
hold on 

How can I find the way to obtain the graph?