\(\underbrace{a+a+a+\cdots+a}_{n\ \text{times}}=a^2b\) and…

$\underbrace{a+a+a+\cdots+a}_{n\ \text{times}}=a^2b$ and $\underbrace{b+b+b+\cdots+b}_{m\ \text{times}}=ab^2$, where a, b, n and m are natural numbers. What is the value of

$\left(\underbrace{m+m+m+\cdots+m}_{n\ \text{times}}\right)\left(\underbrace{n+n+n+\cdots+n}_{m\ \text{times}}\right)$?