Just b I need to know, I need explanation also.

Answer:
[tex] \implies \: 2.6851 \text{ \: ft}[/tex]
[tex] \\ [/tex]
Step-by-step explanation:
[tex] \boxed{\boxed{ \blue\bigstar \red{ \bold{ \: \: math \: \: }} \blue\bigstar}}[/tex]
[tex] \pink{\implies = \sqrt{ {36.1}^{2} - {36}^{2}} } [/tex]
[tex] \orange{ \implies = \sqrt{1303.21} - 1.296}[/tex]
[tex] \green{ \implies = \sqrt{7.21} }[/tex]
[tex] \red{ \implies = 2.6851 \: \text{ft}}[/tex]