Calculate the standard Gibbs energy (\( \Delta G^\circ \)) of the following reaction at 25°C:
\[
\text{Au}(s) + \text{Ca}^{2+}(1M) \to \text{Au}^{3+}(1M) + \text{Ca}(s)
\]
\[
E^\circ_{\text{Au}^{3+}/\text{Au}} = +1.5 \, \text{V}, \quad E^\circ_{\text{Ca}^{2+}/\text{Ca}} = -2.87 \, \text{V}
\]
Predict whether the reaction will be spontaneous or not at 25°C.
[1 F = 96500 C mol\(^{-1}\)]