1.55 Perform the following calculations. Answers must have the correct number of significant figures. \text { (a) }\left(8.20 \times 10^{2}\right)+\left(3.75 \times 10^{4}\right) \text { (b) }\left(5.21 \times 10^{-2}\right)+\left(2.74 \times 10^{-3}\right)

\text { (c) }\left(1.01 \times 10^{-4}\right)+\left(7.23 \times 10^{-3}\right)