Find an Equation of the Parabola Described $x ^ { 2 } = 84 y$

Multiple Choice

Find an equation of the parabola described.
-Focus at (0, 21) ; directrix the line y = -21

A) $x ^ { 2 } = 84 y$
B) $y ^ { 2 } = 84 x$
C) $y ^ { 2 } = 21 x$
D) $x ^ { 2 } = - 84 y$