If the shortest distance of the parabola \( y^2 = 4x \) from the centre of the circle \( x^2 + y^2 - 4x - 16y + 64 = 0 \) is \( d \), then \( d^2 \) is equal to:
\( 36 \)
\( 20 \)
\( 24 \)
\( 16 \)