Levels for the trade are:
Entry = Rs 339+
Short term target (Intraday or 1-2 day target after the breakout)
Target 1 = Rs 349.95
Medium term targets (2-5 weeks after breakout)
Target 2 = Rs 373.7
Target 3 = Rs 400
1. If the breakout is weak i.e. not with a strong , it may fail. However the first target should be still achievable.
2. It may retest the trend-line one final time before giving the breakout.
3. A reversal from Rs 338-339 is also possible in case of a sell-off. Wait for the breakout.
400 is a critical level and may act as a strong resistance hence giving us a target to book profits.
Holding the stock would depend on your trading style. I'd suggest that if you're a conservative trader you can book partial profits(exit 30-40% of your position) and then wait for the remaining targets.