[tex]\qquad \qquad\huge \underline{\boxed{\sf Answer}}[/tex]
Here's the solution ~
[tex]\qquad \sf \dashrightarrow \: 5P \times 7 {P}^{3} [/tex]
[tex]\qquad \sf \dashrightarrow \: (5 \times 7)(P \times P {}^{3} )[/tex]
[tex]\qquad \sf \dashrightarrow \: 35(P {}^{ 1 + 3} )[/tex]
[tex]\qquad \sf \dashrightarrow \:35 P {}^{4} [/tex]