I'm using excel Solver for this question, but the solver cannot find a feasible solution(my work below).

Young Energy operates a power plant that includes a coal-fired boiler to produce steam to drive a generator. The company can purchase different types of coals and blend them to meet the requirements for burning in the boiler. The following table shows the characteristics of the different types of coals:

The total BTU/pound across four coal types must be at least 15,500. In addition, the total ash content can be at most 12.7% and the moisture content at most 9.4%. Develop and solve a linear optimization model to find the best coal blend for Young Energy.

\begin{tabular}{ccrrr} \hline Coal Type & BTU/lb & % Ash & % Moisture & Cost ($/lb) \\ \hline A & 11,500 & 13% & 10% & $2.49 \\ B & 11,800 & 10% & 8% & $3.04 \\ C & 12,200 & 12% & 8% & $2.99 \\ D & 12,100 & 12% & 8% & $2.61 \\ \hline \end{tabular} \begin{tabular}{ccrrr} \hline Coal Type & BTU/lb & % Ash & % Moisture & Cost ($/lb) \\ \hline A & 11,500 & 13% & 10% & $2.49 \\ B & 11,800 & 10% & 8% & $3.04 \\ C & 12,200 & 12% & 8% & $2.99 \\ D & 12,100 & 12% & 8% & $2.61 \\ \hline \end{tabular}