$x + y + z = 15$ if $9,\;x,\;y,\;z,\;a$ are in $A.P.$; while $\frac{1}{x} + \frac{1}{y} + \frac{1}{z} = \frac{5}{3}$ if $9,\;x,\;y,\;z,\;a$ are in $H.P.$, then the value of $a$ will be

  • [IIT 1978]
  • A

    $1$

  • B

    $2$

  • C

    $3$

  • D

    $9$

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