Vehicle mirror calculation for class4

I am trying to calcualed the truck mirror class 4 , what should be things i should kept in mind while calcualating the mirror dimension

% i know the basic equation 
R= 2 %Rear view of mirror of moving car in meter
u= -3.5 % vehicle from behind distance 

f =R/2 % focal length of the image 

% postion  of the image relative to the vehicle 
v = ((1)+ (1/u)) % image is form behind the mirror


%positon of the mirror 
m= ((-v)/u) % magnification  +ve image is formed virtua and erect