In the Equation $\vec { M } + \vec { v } = \vec { P } + \vec { Y } _ { R }$

In the equation $\vec { M } + \vec { v } = \vec { P } + \vec { Y } _ { R }$ , what does $\bar { Y } _ { R }$
Stand for?

A) real GDP
B) nominal GDP
C) growth in real GDP growth
D) growth in nominal GDP growth