_lcp5.png" alt="../../../../fig/mpt/modules/solvers/mpt_call_lcp5.png"> must be invertible in order to express basic variables as 
        a function of non-basic variables, i.e.
        <p class="programlistingindent"><img src="../../../../fig/mpt/modules/solvers/mpt_call_lcp47.png" alt="../../../../fig/mpt/modules/solvers/mpt_call_lcp47.png"></p>
        With the substitution
        <p class="programlistingindent"><img src="../../../../fig/mpt/modules/solvers/mpt_call_lcp48.png" alt="../../../../fig/mpt/