As per given by the question,
There are given that a right angle trinfle BRG.
Now,
From the tringle BRG, the hypotenuse is 28 ft, and angle B is 30 degree.
To find the length RG, first let RG is x.
Now,
Here find the value of x, use sine trigonometric function.
So,
![\sin 30^(\circ)=(RG)/(BG)](https://img.qammunity.org/2023/formulas/mathematics/college/cpewg2xkg843y6gaiy5wopanhvfxvibxmr.png)
Then,
Put the value 28 for BG and x for RG.
So,
![\begin{gathered} \sin 30^(\circ)=(RG)/(BG) \\ \sin 30^(\circ)=(x)/(28) \\ (1)/(2)=(x)/(28) \\ 2x=28 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/reqg186yynehsmqdqyk6to8n3dm2d20t30.png)
Now,
![\begin{gathered} 2x=28 \\ x=(28)/(2) \\ x=14\text{ ft} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/iztc87huy04rvjs0e6tegmpqazzfi2hcbc.png)
Hence, the option first is correct.