You are applying a Sharpe style analysis model to better understand the returns generated by a long-only small cap value fund that uses no leverage. In order to accurately capture the constraints faced by the portfolio managers, it is necessary to assure that the coefficients are specified in the following way:

a. positive or negative but not required sum to 1

b. positive only but not required to sum to 1

c. positive or negative and sum to 1

d. positive only and sum to 1