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5 km/hr

4 km/hr

3 km/hr

1km/hr

C. 3 km/hr

let rate upstream=x km/hr and rate downstream=y km/hr.

Then, 40/x +55/y =13… (i) and 30/x +44/y =10

Multiplying (ii) by 4 and (i) by 3 and subtracting, we get:11/y=1 or y=11.

Substituting y=11 in (i),we get:x=5.

Rate in still water =1/2(11+5)kmph=8kmph.

Rate of current=1/2(11-5)kmph=3kmph