Monitor

FIG. 1 is a front perspective view of a monitor, showing our new design; FIG. 2 is a front view thereof; FIG. 3 is a rear view thereof; FIG. 4 is a left-side view thereof; FIG. 5 is a right-side view thereof; FIG. 6 is a top view thereof; FIG. 7 is a bottom view thereof; and, FIG. 8 is a rear perspective view thereof. The broken lines illustrating portions of the monitor form no part of the claimed design.