Assertion: The value of $x+y+z$ is 15 if $a, x, y, z$ $b$ are in A.P., while the value of $\frac{1}{x}+\frac{1}{y}+\frac{1}{z}$ is $\frac{5}{3}$ if $a, x, y, z, b$ are in H.P. The values of $a$ and $b$ are 9,1 respectively. Reason: The sum of $n$ A.M.s between two quantities is equal to $n$ times their single mean.