P $6\mathrm{.}49$

Two filters are in cascade. At a given frequency f$1$f$1,$ the transfer function values are $|$H$1($f$1)|$dB$|$H$1($f$1)|$dB $=-25$ and $|$H$2($f$1)|$dB$|$H$2($f$1)|$dB $=+40.$