  We examine the black hole bomb model which consists of a rotating black hole
of five-dimenensional minimal ungauged supergravity and a reflecting mirror
around it. For low-frequency scalar perturbations, we find solutions to the
Klein-Gordon equation in the near-horizon and far regions of the black hole
spacetime. To avoid solutions with logarithmic terms, we assume that the
orbital quantum number $ l $ takes on nearly, but not exactly, integer values
and perform the matching of these solutions in an intermediate region. This
allows us to calculate analytically the frequency spectrum of quasinormal
modes, taking the limits as $ l $ approaches even or odd integers separately.
We find that all $ l $ modes of scalar perturbations undergo negative damping
in the regime of superradiance, resulting in exponential growth of their
amplitudes. Thus, the model under consideration would exhibit the superradiant
instability, eventually behaving as a black hole bomb in five dimensions.
