Answer:
The radius is 9.0 units
Step-by-step explanation:
we know that
In the right triangle of the figure ABC
Applying the Pythagorean Theorem

substitute the given values

solve for AB

Remember the the side AB of right triangle represent the radius of the circle
therefore
The radius is 9.0 units
When you write an equation in the slope-intercept form

the two coefficients m and b represent, respectively, the slope and the intercept.
So, in your case, m=1/4 and b= -7, which leads to the equation

F x L = 3x10^10
L = 1x10^-11
F= 3x10^10 / 1x10^-11 = 3x10^21 unit
Because, 9 x 9 = 81. Hope I helped!