Find the Value of K That Makes F(x) = Kx $1 \leq x \leq 2$

Multiple Choice

Find the value of k that makes f(x) = kx a probability function on the interval $1 \leq x \leq 2$ .

A) $\frac { 4 } { 5 }$
B) $\frac { 2 } { 5 }$
C) $\frac { 2 } { 3 }$
D) $\frac { 6 } { 5 }$
E) none of these