Determine whether the following can be probability distributions of a random variable which can take on only the values \(1,2,3\), and 4 .

(a) \(f(1)=0.19, \quad f(2)=0.27, \quad f(3)=0.27\), and \(f(4)=0.27\)

(b) \(f(1)=0.24, \quad f(2)=0.24, \quad f(3)=0.24, \quad\) and \(f(4)=0.24\)

(c) \(f(1)=0.35, \quad f(2)=0.33, \quad f(3)=0.34\), and \(f(4)=-0.02\).