Assume that the marginal benefit received from a good is less than the marginal opportunity cost of production. from this information, we can suppose that:

We can suppose then that the good is being over produced and there is some sort of inefficiency which led to over production of the good

Explanation:

When the marginal benefit of the good is less than the marginal opportunity cost this means that it cost us more to make the last unit compared to the benefit we got from the unit when consumed. In such a case, it is optimal to reduce the production of the good as the marginal cost of production has moved from the optimal point of the curve to the right which means each product manufactured now would lead to increase in marginal cost.

In such a case less production of the good would decrease welfare leading to overproduction of the good.