Hello Everyone,

I have had an Error 148 when I tried to run my code for homework. It’s really confusing, and I can’t find the problem with my equation expression. Thanks for your help!

sets

t periods /0*50/

;

alias (t,tt);

parameters

a demand curve intercept /8/

b demand curve slope /0.4/

C marginal extraction cost /2/

r discount rate /0.05/

Q total resource available /40/

lambda marginal user cost

;

variables

x(t) quantities extracted per period

p(t) price of extracted resource per period

nb present value of net benefit

;

equations

obj_func objective function

dem_curve(t) demand curve

cons total available resource

;

obj_func… nb =e= sum(t, (exp(-r*t)) * (x(t)*(a-((0.5*b)*x(t)) -c)));
dem_curve(t)… p(t) =e= a - (b*x(t));

cons… Q =e= sum(t,x(t));

model extraction /obj_func, dem_curve, cons/;

- set lower bounds to avoid errors and ensure a meaningful solution

x.lo = 0;

p.lo = 0;

solve extraction using nlp maximizing nb;

lambda(t)$(x.l(t) > 0) = exp(-r*t)*(a - b*x(t)-c);

display lambda;