Function $g$ is defined as follows: This function has an inverse. What is g^-1(-7)

Function $g$ is defined as follows: $g(x) = \left\{ \begin{array}{cl} 5x^2 & \text{if } x \le -3, \\ 21+x& \text{if }-3 < x \le 10, \\ 2-\sqrt{x}& \text{if }x > 10. \end{array}\right.$This function has an inverse.   What is g^-1(-7)