Answer:
A,d,e not sur tho
Step-by-step explanation:
The top 4 firms have (23 +22 +18 +12)% = 75% of the market.
The 4-firm concentration ratio is 0.75 or 75%.
Answer:
Option B is correct
the degree of rotation is, 
Step-by-step explanation:
A rotation matrix is a matrix that is used to perform a rotation in Euclidean space.
To find the degree of rotation using a standard rotation matrix i.e,

Given the matrix: 
Now, equate the given matrix with standard matrix we have;
= 
On comparing we get;
and
As,we know:

we get;

and

we get;

Therefore, the degree of rotation is, 