Two bottles A and B have radii RA and RB and heights hA and hB respectively with RB=2RA and hB=2hA. These are filled with hot water at 60oC. Consider that heat loss for the bottles takes place only from side surfaces. If the time the water takes to cool down to 50oC is tA and tB for bottles A and B, respectively, then tA and tB are best related as.