Correct. The students who improved were Jessica, Bob, and Lydia, because their retake bars were higher than their test bars. Jessica's improvement was $\displaystyle{100}-{90}={10}\usepackage{cmbright}\Huge\$ . Bob's improvement was $\displaystyle{80}-{70}={10}\usepackage{cmbright}\Huge\$ . Lydia's improvement was $\displaystyle{85}-{65}={20}\usepackage{cmbright}\Huge\$ . Lydia had the greatest improvement.