Needing a win to qualify for the knock-outs, Bengal skittled group toppers Assam for only 95 runs in 33.4 overs and then knocked off the runs in only 17.5 overs.
While seamer Veer Pratap Singh did the trick with the ball grabbing four for 31, their No 1 batsman Manoj Tiwary smashed an unbeaten 61 off 62 balls to ensure that Bengal get a bonus point.
Assam topped the group with 14 points and Bengal came second with 12 but will be playing in the quarter-finals by virtue of winning the title in the last edition.
All the Bengal bowlers chipped in with impressive performances. Veer Pratap was well complemented by skipper Laxmi Ratan Shukla who took two for 13.
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In reply, Bengal rode on a 72-run partnership for the fourth wicket between Tiwary and Anustup Majumdar who gave him support scoring 12.
Tiwary again showed the gulf between him and other Bengal batsmen as he singlehandedly took the Assam bowlers to the cleaners hitting eight fours and two sixes even after the team was in shambles at 26 for three.
Brief Scores: Assam 95 all out in 33.3 overs (Shib Shankar Roy 20, VP Singh 4/31, LR Shukla 2/13).
Bengal 98/3 in 17.5 overs (Manoj Tiwary 61 no).
Bengal won by 7 wkts. Points: Bengal 5; Assam -1.
Bengal and Assam qualify for knock-outs.