Three resistors with the values of R_1, R_2, and R_3 are connected in parallel. Which of the following expresses the total resistance e, R_eq of the resistors?
a.) R_eq = R_1 + R_2 + R_3
b.) R_eq = (1/R_1 + 1/R_2 + 1/R_3)
c.) R_eq = R_1 = R_2 = R_3
d.) R_eq = (1/R_1 + 1/R_2 + 1/R_3 ) ^-1