Question: Too long evaluation

Hi, I'm working on fitting model. For some reason is taking way too long to evaluate it actually hasn't finished it at all. Im running on i7. Thanks for any help. this is my code: 

> X := Vector([0, 170, 0]);
              
> Y := Vector([0, 11, 56]);
               

Q(t) := -(36788*76)*(.28*K*p/(-p-exp(-r*t)*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*t)*K-r*exp(-r*t)*p)/(-p-exp(-r*t)*K+exp(-r*t)*p)^2)*exp(.28*t*p*K/(-p-exp(-r*t)*K+exp(-r*t)*p))-(80457*76)*(.28*K*p/(-p-exp(-r*(t-1))*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*(t-1))*K-r*exp(-r*(t-1))*p)/(-p-exp(-r*(t-1))*K+exp(-r*(t-1))*p)^2)*exp((.28*(t-1))*p*K/(-p-exp(-r*(t-1))*K+exp(-r*(t-1))*p))-(92096*76)*(.28*K*p/(-p-exp(-r*(t-2))*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*(t-2))*K-r*exp(-r*(t-2))*p)/(-p-exp(-r*(t-2))*K+exp(-r*(t-2))*p)^2)*exp((.28*(t-2))*p*K/(-p-exp(-r*(t-2))*K+exp(-r*(t-2))*p))-(78400*76)*(.28*K*p/(-p-exp(-r*(t-3))*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*(t-3))*K-r*exp(-r*(t-3))*p)/(-p-exp(-r*(t-3))*K+exp(-r*(t-3))*p)^2)*exp((.28*(t-3))*p*K/(-p-exp(-r*(t-3))*K+exp(-r*(t-3))*p))-(70040*76)*(.28*K*p/(-p-exp(-r*(t-4))*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*(t-4))*K-r*exp(-r*(t-4))*p)/(-p-exp(-r*(t-4))*K+exp(-r*(t-4))*p)^2)*exp((.28*(t-4))*p*K/(-p-exp(-r*(t-4))*K+exp(-r*(t-4))*p))-(65093*76)*(.28*K*p/(-p-exp(-r*(t-5))*K+exp(-r*t)*p)+.28*t*p*K*(r*exp(-r*(t-5))*K-r*exp(-r*(t-5))*p)/(-p-exp(-r*(t-5))*K+exp(-r*(t-5))*p)^2)*exp((.28*(t-5))*p*K/(-p-exp(-r*(t-5))*K+exp(-r*(t-5))*p);

> NonlinearFit(Q(t), Y, X, t);