Question 7 [10 marks] A typical houseplant produces oxygen (from carbon dioxide) in varying amounts, depending on the amount of light and water. Suppose a medium Norfolk Island pine produces 7.5 mL of oxygen per hour when exposed to normal sunlight. Thirty-five Norfolk Island pines are selected at random, and the oxygen output is carefully measured for each. Assume =1.75 mL/hr

a. [3 marks] What is the probability that the sample mean oxygen produced is less than 7 mL/hr?

b. [3 marks] What is the probability that the sample mean oxygen produced is between 7.25 and 7.5 mL/hr?

c. [4 marks] Suppose each plant is exposed to a new high-intensity grow light and the sample mean oxygen produced for the 35 plants is 8.1 mL/hr. Is there any evidence that the new lamp has increased oxygen output?