Getting error- cannot differentiate equationequation; while solving two nonlinear equations using solvenumeric in MuPAD

I need to solve following two equations for solving effective mass of nucleons in an infinite nuclear matter:

y=1862-x/2500 and,
x=0.32*y[(0.00076+y^2)^1/2 - y*ln(0.00076+(0.00076+y^2)^1/2)/y].

I wrote the following code in MuPAD:

numeric::solve([eqn 1, eqn 2],[x=0..0.5,y=0..1], MultiSolutions);

I wrote the two equations exactly as above! But, I am getting an error: cannot differentiate equation [numeric:fsolve]. Please help!!!