To calculate an answer to the correct number of significant figures, you must complete all calculations first and then round your final answer as the very last step. in part c, you are asked to calculate the volume of a rectangular prism that has a length of 5.6 cm, a width of 2.1 cm, and a height of 6.6 cm. you can calculate the volume of a prism by multiplying the area of the base times the height. you already calculated the area of the base as 2.1cm×5.6cm in part a.