The Standard Molar Free Energies of Formation of NO₂(g) and N₂O₄(g)

The standard molar free energies of formation of NO₂(g) and N₂O₄(g) at 25°C are 51.84 and 98.28 kJ/mol, respectively. What is the value of K_p (in atm) for the reaction written as follows at 25°C? 2NO₂ N₂O₄

A) 8.84
B) 1.17 * 10⁴
C) 1.37 * 10⁸
D) 7.31 *10^-9
E) 0.113