Answer
There are necessary 9.2 hours of sitting to burn off the kilocalories in this meal.
Work Step by Step
According to the Table 3.10 (Page 73), a 70.0 kg person, while sitting, burns 100 kcal per hour. We can use this as a conversion factor.
As we have calculated in 3.62b, the total kilocalories in this meal is equal to 920 kcal.
$920 kcal \times \frac{1h}{100kcal} = 9.2 h$