(a) An average person has 5.6L of blood. The typical concentration of red blood cells is 5 million cells/mL of blood. New red blood cells are created by stem cells in one's bone marrow at a rate of 2700 cells per second. What is the average life span (residence time) of a red blood cell? (b) On average, the human heart pumps 25mL of blood each time it beats and it beats 72 times per minute. How much time does a red blood cell require to complete a loop of the circulatory system, on average? (c) You are in a queue for a single-rider water slide. A sign indicates the wait time from your position is 60 minutes. One rider exits the slide every 45 seconds. How many riders are on line in front of you? (d) Each August, 20 new students join a PhD program. During a typical year, 16 students graduate with PhD degrees and 4 students leave without PhD degrees; some students quit after earning a Masters degree and some students fail the qualifying exam and are asked to leave. The average population of the PhD program is 96 students. Calculate the residence time for a student in this PhD program. (e) Assume that each year two students are expelled after one year and two students earn Masters degrees after two years. Calculate the average time required to earn a PhD degree. Hint: draw a process flow diagram in which 20 students/year "flow" into the "PhD year 1" unit, 18 students/year flow into the "PhD year 2" unit, etc. How many "PhD year x " units are needed such that the PhD process comprises 96 students