$($a$)$ A person's blood pressure is measured to be $115+-4mmHg.$ What is its percent uncertainty? $($Express your answer to

the correct number of significant figures and proper units. Use unrounded values in your calculations.$)$

$4\mathrm{.}0$

$($b$)$ Assuming the same percent uncertainty, what is the uncertainty in a blood pressure measurement of $84mmHg?$

$($Express your answer to the correct number of significant figures and proper units. Use unrounded values in your

calculations.$)$