Please explain which option is correct and why. Also, please explain why the other options are incorrect.

In the following diagram you are given two technologies, A and B, which can produce 100 metres of cloth. Technology A uses 1 worker and 4 tonnes of coal, while technology B uses 4 workers and 2 tonnes of coal. The diagram also depicts three examples of isocosts, NM, GF and JH. The wage cost and the price of coal are denoted by wand p, respectively. Your firm competes with many other firms in this cloth market. In period 1, the wage cost and the price of coal are (w, p) = (10, 20) and the price of the cloth is 2 per metre. All firms employ technology B in period 1. In period 2, the wage cost and the price of coal change to (w, p) = (20, 10). Which of the following statements is correct?