Selective serotonin reuptake inhibitor. Selective serotonin reuptake inhibitors (SSRIs), also known as serotonin-specific reuptake inhibitors or serotonergic antidepressants,[1] are a class of drugs that are typically used as antidepressants in the treatment of major depressive disorder and anxiety disorders.
Then you're looking for the midpoint! The midpoint of a line segment is the point located midway between the endpoints of the line segment. This tutorial tells you about the midpoint of a line segment.
The midpoint, or class mark, of a class is the sum of the lower and upper limits of the class divided by 2. The midpoints are often used for estimating the average value in each class. Once you find the first midpoint, you can add the class width to it to find the remaining midpoints.