You are doing a calculation in which you must add two quantities \(A\) and \(B\). You know that \(A\) can be expressed as \(A=\frac{1}{2} a t^{2}\), where \(a\) has units of meters per second squared and \(t\) has units of seconds. No matter what the expression for \(B\) is, what must the units of \(B\) be?