lambda .* P <= mu * phi so
lambda .* P / mu <= phi
With lambda, P, and mu all being constants, this does not need to be written as a linear constraint. Instead, it can be written as lower bound: phi >= lambda .* P / mu so
x0 = .... %starting point
A = []; b = [];
Aeq = []; beq = [];
LB = lamda .* P ./ mu; UB = inf(1,48);
fmincon( fun, x0, A, b, Aeq, beq, LB, UB )
If you prefer to implement it as a linear constraint (perhaps because you are using a different minimizer) then
A = -eye(48); B = lambda .* P ./ mu;
