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 $E$ $= 500 , R = 50$ and $\mathrm { I } = 2$ .

A) $\quad k = - 5$
B) $\quad k = - 500$
C) $\quad k = 500$
D) $\quad k = 2$
E) $\quad k = 5$