Question 10The *harmonic mean* of a set of non-zero numbers is the reciprocal of the average of the reciprocals of the numbers. What is the harmonic mean of $1,$ $2,$ and $4?$$ \dfrac{3}{7} $$ \dfrac{7}{12} $$ \dfrac{12}{7} $$ \dfrac{7}{4} $$ \dfrac{7}{3} $