I'm trying to resolve the convection-diffusion equation coupled with the continuity equation. I wrote this next code

A = 4;
h = 190;
Media = -60*h/190;
DesEst = 0.15*h;
Distribucion = A*PDF[SkewNormalDistribution[Media, DesEst, -5], x];
d1 = 17;
s3 = NDSolve[{D[c[x, t], t] - d1*D[c[x, t], x, x] + 
     V[x]*D[c[x, t], x] == 0, c[x, t]*D[V[x], x] == 0, 
   c[x, 0] == Distribucion, 
   c[-10*DesEst, t] == Distribucion /. x -> -10*DesEst, 
   DirichletCondition[V[x] == V[5000], x == -10*DesEst], 
   Derivative[1, 0][c][-10*DesEst, t] == 0}, {c[x, t], 
   V[x]}, {x, -10*DesEst, 5000}, {t, 0, 70}]

But I received the next message

NDSolve::overdet: There are fewer dependent variables, {c[x,t]}, than equations, so the system is overdetermined.

I don't understand what's the problem if I'm declaring c and V like dependent variables to resolve. Does anybody know how to fix it?