***all negative signs should be in superscript***

Question

Consider the following reactions:
R-+ Q —> Q- + R (non-spontaneous)
S + Q- —> Q + S- (non-spontaneous)
S + T- —> T + S- (spontaneous)
R- + U —> U- + R (spontaneous)

Which of the following reactions would be spontaneous?
1) R- +T
2) R- + S
3) Q + U-
4) U + T-