steriochemistry

ans marked
but my doubt here is that if we go by formula ans sud be 2^n1 +2^n1/2 right ?? then here n=1 that is only one steriocentre that is pi bond then ans is coming 2 ........and also if we go through physical method then possiblty is one time cis and second is trans ....right

@kingkong
Your formula is applicable for geometrical isomers and you are taking n=1 (No. of the double bond). But, there is a chiral carbon also. So, you will get the wrong answer by that formula.
There are two stereocentres n=2 and use 2^n for total isomers.
And by physical method Cis & Trans and for chiral carbon, original and its mirror image.