Epidemiologists decided to investigate the effect of sunscreens on sunburns. They ran an epidemiologic study to see the association of sunscreens and sunburns. Overall, 460 people have enrolled in the study. Investigators randomly allocated 230 people to the treatment group (sunscreens) and 230 to the control group (placebo). They exposed those 460 people to the high mountain trail on a sunny day. At the end of the study, 30 people developed sunburns in the sunscreen group and 130 people developed sunburns in the placebo group. What is the relative risk of sunburns in the sunscreen treatment group compared with the control group in this study