Perimeter and area

$Diagonal\space =\space \sqrt{l^2+b^2},\space area=lb.$

$\sqrt{l^2+b^2}=25\space \Rightarrow\space l^2+b^2=625....\boxed{1}$

$lb=168\space \Rightarrow\space 2lb=336...\boxed{2}$

Adding $\boxed{1}$ and $\boxed{2}$ , we get: $l^2+b^2+2lb=625+336=961\Rightarrow\space l+b=\sqrt{961}=31....\boxed{3}$ Subtracting $\boxed{1}$ and $\boxed{2}$ , we get: $l^2+b^2-2lb=625-336=289\Rightarrow\space l-b=\sqrt{289}=17....\boxed{4}$ From the system of equations $\boxed{3}\space and\space \boxed{4},$ we get: $l=24\space \text{and}\space b=7$ The rest is left to the reader.