Question: Problem ploting a function

Hello everyone. 

I have the followinf code but when I try to plot I am receiver an error. Please, someone coulg give me a hint?

A := 20

B := 10.37

P := 60*24*60

omega := 2*Pi/P

alpha := 0.7*10^(-6)

phi := 3.61

Profundidade := 0.1;

ntotal := 1

theta(z, t, k, C) :=A + sum(B*exp(z*sqrt(1/2*omega*m*C/k))*sin(omega*m*t - z*sqrt(1/2*omega*m*C/k) + phi), m = 1 .. 5);

SensibilidadeK := (z, t, k, C) -> diff(theta(z, t, 1, 1), k);
GrafE := plot(eval(SensibilidadeK*(Profundidade, t, k, C), [k = 1, C = 1]), t = 0 .. 86400, color = blue, legend = k, labels = ["Tempo [s]", "Coeficiente de Sensibilidade"], labeldirections = ["horizontal", "vertical"])

this is the error that I received: Warning, expecting only range variable t in expression SensibilidadeK*(.1, t, 1, 1) to be plotted but found name SensibilidadeK