The Reaction Below Has a K_c Value of 61 M^-2

The reaction below has a K_c value of 61 M^-2. What is the value of K_p for this reaction at 500 K? N₂(g) + 3H₂(g) ⇌ 2NH₃(g)

A) 15 bar^-2
B) 61 bar^-2
C) 28 bar^-2
D) 3.6 × 10^-2 bar^-2
E) 1.9 × 10^-2 bar^-2