Nathan and Thomas Were Both Just Convicted of Felonies and Sentenced

Nathan and Thomas were both just convicted of felonies and sentenced to prison. Nathan was convicted of attempted murder. Thomas was convicted of stealing multiple vehicles. Both offenders have juvenile records but this is their first conviction in adult court. Nathan is being sent to a state institution. Thomas is being sent to a private prison in the state.
-The state utilizes private prisons for inmates classified as non-violent offenders. The argument behind this approach is that private prisons are more cost-effective than state run prisons. What does the current research say about the cost effectiveness of private prisons in comparison to state prisons?

A) Evaluation studies have been inconclusive.
B) Evaluation studies show that private prisons can do the same job as a public prison for half the cost.
C) Evaluation studies show that private prisons can do the same job as a public prison for one-fourth the cost.
D) Evaluation studies show that public prisons can do the same job as a private prison for half the cost.