(b)
$\int_{- 1}^{15}{sgn\left( \left\{ x \right\} \right)dx = \int_{0}^{16}{sgn\left( \left\{ x - 1 \right\} \right)dx}}$ (by property)
$= \int_{0}^{16}{sgn\left( \left\{ x \right\} \right)dx}$
$= 16\int_{0}^{1}{sgn\left( \left\{ x \right\} \right)dx =}16\int_{0}^{1}{sgn(x)dx}$
$= 16\int_{0}^{1}{1 \bullet dx = 16}$