Question:solving 4 equations

Question:solving 4 equations

Maple

hi, i want to solve these 4 equations and i have two problems

1-when i use the function SOLVE , the output is empty brackets, why?

2-how can i add constrains or inequalities to make maple consider them in the solution

the solve line is

solve({e^(-z[11]/t[1])*(p[21]*e^(-z[21]/t[1])+p[22]*e^(-z[22]/t[2])) = t[1]*(1-w-u[11])/(w*p[11]), e^(-z[12]/t[2])*(p[21]*e^(-z[21]/t[1])+p[22]*e^(-z[22]/t[2])) = t[2]*(1-w-u[12])/(w*p[12]), e^(-z[21]/t[1])*(p[11]*e^(-z[11]/t[1])+p[12]*e^(-z[12]/t[2])) = t[1]*(1-w-u[21])/(w*p[21]), e^(-z[22]/t[2])*(p[11]*e^(-z[11]/t[1])+p[12]*e^(-z[12]/t[2])) = t[2]*(1-w-u[22])/(w*p[22])}, [z[11], z[12], z[21], z[22]])

and the constrains that i want maple to consider are

u[11].z[11] = 0

u[12].z[12] = 0

u[21].z[21] = 0

u[22].z[22] = 0

z[11] >= 0

z[12] >= 0

z[21] >= 0

z[22] >= 0

u[11] >= 0

u[12] >= 0

u[21] >= 0

u[22] >= 0

i tryed to add these constrains to the solve line as othe equations but maple still gives me empty brackets

plz help me

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