What is the activation energy for the reverse reaction?

Question

The reaction A(g)+B(g)-->C(g) + D(g) + 30 kcal has a foward activation energy of 20 kcal. What is the activation energy for the reverse reaction?

30, 20, 10, or 50 kcal

thank you!

Answer 1

Assuming there's nothing else involved in the reverse reaction, it should be 50 kcal (20 + the 30 released that you have to put back in).