$$
begin{align*}
m_{tot}&=m_{bass}+m_{{rock} {cod}}+m_{salmon}\
&=1.07 text{kg}+6.0 text{kg}+6.05 text{kg}\
&=quadboxed{13.12 text{kg}}\
end{align*}
$$

$$
begin{align*}
P&=2a+2b\
&=2(a+b)\
end{align*}
$$

where $a$ is width and $b$ is height.

So, the perimeter of a sheet of paper with $a=18.1 text{cm}$ and $b=25.2 text{cm}$ is

$$
begin{align*}
P&=2(18.1 text{cm}+25.2 text{cm})\
&=quadboxed{86.6 text{cm}}\
end{align*}
$$