A study was conducted of pleas made by 1,348 criminals. Among those criminals, 956 pleaded guilty and 392 of them were sentenced to prison. Among 72 other criminals who pleaded not guilty, 58 were sent to prison (based on data from "Does It Pay to Plead Guilty?" by Brereton and Casper, Law and Society Review, Vol. 16, No. 1).

a. What percentage of the criminals pleaded guilty?

b. What percentage of the criminals were sent to prison?

c. Among those who pleaded guilty, what is the percentage who were sent to prison?

d. Among those who pleaded not guilty, what is the percentage who were sent to prison?