Let $a$ and $b$ be two positive integers such that $a=p^3{q}^4$ and $b=p^2{q}^3$, where $p$ and $q$ are prime numbers. If H.C.F $\left(a, b\right)=p^m{q}^n$ and L.C.M$\left(a, b\right)=p^r{q}^s$, then $\left(m+n\right)\left(r+s\right)$