well i ud 1 thng........

a number of factors determinf which sort of reaction it ud be....

SN1 or SN2....

1. steric faactor

2. polarity

3. temperature (carbocations are more stable in higher temp.)

4. hyperconjugation...                             ( C+ stability.. see that)

5. conjugation....

6. strenght of nucleophile..

many....

we hve to take many into account.... b4 deciding wat sorta reaction it ud be and also decide wat to gve more prefrence over other depending on situations....

but seeing this reaction it will hve to be SN2...

or else if SN1... CH3- CH2 -I... us hve formed ... as C+ is more stable thre....

but still we hve to see other factors... as nothng is gven it is SN2

Cheers!!!!!!!