_Note for mods: I already submitted a question id like to update but i cant seem to find it now_

I have been running the following sage code on cocalc.com to solve a standard utility maximization problem that is in an intermediate microeconomics course. However I'm having difficulty solving these problems in the context of SAGE.

Below is the code that I have run to solve the problem and so far I believe its correct.

x,y,l=var('x,y,l')

U=x^0.7*y^0.3;U
m=2*x+2

*y; m*

solve (m==4000,y)

L=U-l(m-4000);L

solve (m==4000,y)

L=U-l

dLdx=L.diff(x);dLdx

dLdy=L.diff(y);dLdy

dLdl=L.diff(l);dLdl

solve([dLdx==0,dLdy==0,dLdl==0],x,y,l)

All my code seems to be running fine, however the last line of:

solve([dLdx==0,dLdy==0,dLdl==0],x,y,l)

is not outputting the final demand equations. Is there any reason why this is happening?