Which one of these is the correct formula for computing the return on a portfolio comprised of unequal amounts of stocks $A,B,$ and $C?$

$R_P=\frac{(w_A{R}_A)+(w_B{R}_B)+(w_C{R}_C)}{3}$

$R_P=(w_A{R}_A)+(w_B{R}_B)+(w_C{R}_C)$

$R_P=\frac{R_A+R_B+R_C}{3}$

$R_D=(w_A+w_B+w_C)[\frac{R_A+R_B+R_C}{3}]$