Approximate the real-number expression. Express the answer in sclentific notation accurate to four significant figures.
(a) $\sqrt{\left|3.45-1.2 \times 10^{4}\right|+10^{3}}$
(b) $\left(1.791 \times 10^{2}\right) \times\left(9.84 \times 10^{3}\right)$