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,
Then,
Put the value 28 for BG and x for RG.
So,
Now,
Hence, the option first is correct.