Alright, lets get started.
As per the scale, 
Means 0.25 '' = 1 ' (symbol '' denotes inches and ' denotes feet)
As per the drawing, the dimention of bedroom is
and
.
Means

converting into feet, we need to divide with 0.25.
Means the first dimension would be : 
Converting
into decimal : 5 + 0.25 = 5.25
Similarly, the second dimension in feet would be : 
Hence the dimension of bedroom will be 14 ft by 21 ft : Option A : Answer
Hope it will help :)