Find the Constant of Proportionality for the Stated Conditions $E$ Varies Jointly With

Multiple Choice

Find the constant of proportionality for the stated conditions: $E$ varies jointly with $I$ and $R$ , and when $E$ $= 3,600 , R = 50$ and $\mathrm { I } = 9$ .

A) $\quad k = - 3,600$
B) $\quad k = 3,600$
C) $\quad k = 8$
D) $\quad k = 9$
E) $k = - 8$