If she is able to achieve her aim, then the robot is very efficient, as it uses as low as 49 joules in filtering 343 litres of air and water.
It will now be a question of what time the robot is able to achieve this feat, if it is able to do it in a time that matches the quality of the work it does, then it will be reasonable to call the robot efficient, and fast too.
Tiger consumes 18lb/day of food. If we want to calculate how much is consumed in 28 days, assuming that rate is consistent, the answer is 18*28 = 504lb of food.
The sample mean is an unbiased estimate of the population
mean. This tells us that the mean of all sample means is equal to the
population mean. Since we know that the population mean is 5.67, we also know
that the mean of sample means is also 5.67.