Answer
a. $4.5 \times 10^5 N$
b. $4.5 \times 10^5 N$
Work Step by Step
a. The total force is atmospheric air pressure multiplied by the area of the table.
$$F=PA=(1.013 \times 10^5 N/m^2)(1.7m)(2.6m)=4.5 \times 10^5 N$$
b. Assuming a very thin table, the atmospheric pressure is the same under the table. The answer is the same.