Question

Seem to have completely forgotten how to do MRS. Can anyone help?

Carol lives for two-periods. Her utility from consumption in periods 1 and 2 is given by
U(C1, C2) = (C1^α)(C2^(1−α), where 0.5 ≤ α ≤ 1. She has income of Y1 and Y2 in periods 1 and
2, respectively, and no initial wealth.

What is her MRS between first and second period?