(c) The normal resting heart rate for adults ranges from 60 to 100 beats per minute (bpm). Generally, a lower heart rate at rest implies more efficient heart function and better cardiovascular fitness. It is known that the heart rate of an adult is normally distributed with a mean of 80 bom and a standard deviation of 20 bpm. (i) Find the proportion of adults whose heart rate is in the normal resting range. (2 marks) (ii) What is the heart rate of an adult who is in the 90th percentile? Give your answer to the nearest whole number. (3 marks) (iii) By using the Empirical Rule, is it rare that a randomly selected adult has heart rate less than 40 bpm? Justify your answer. (3 marks) (iv) Tachycardia is a condition that makes a person's heart beat more than 100 times per minute. A hospital obtained the heart rates of 500 adult patients. Estimate the number of patients in the sample who could have tachycardia. Give your answer to the nearest whole number