a$)$ Suppose that the Table $1$ below gives the number of patients

registered with a doctor who have a health condition listed in the

table and a particular tendency with respect to their blood pressure.

Table $1$

Blood Pressure

Low

High

Primary

Hyper$-$tension

Secondary

Hyper$-$tension

Total number of

patient

s

Dementia $31532858$

Stroke $210171140$

Type $2$

Diabetes $04124056$

Mobility Problems $216231859$

Total number

of patients $7458477213$

Suppose for each cell in the table the average bodyweight of the

corresponding group of patients can be queried. Given that no patient

may know another patient$$s bodyweight explain why the minimum

query set size is three.