3.5x10^4
lets break it down
10^4= 10x10x10x10 so 10,000
so therefore 3.5x 10,000= 35,000
(if i am wrong please tell me and ill try to fix my mistakes)
Answer: 
Step-by-step explanation:
Slope of two lines that are perpendicular to each other is 1.
If one line is
, then its slope = 3 [by comparing to the linear equation y= mx+c, here m=3]
Let n be the slope of the required line, then

Equation of line with slope n and passers through (a,b) is

Equation of line with slope n=
and passes through point ( 0,-4) :

Hence, Required equation : 
You just have to arrange the equation such that the p is the only term at the left hand side of the equation. Express it in terms of r and m.
r = 1/2*m²*p
Divide both left and right hand side equations by 1/2*m²
p = r/(1/2 *m²)
Take the reciprocal of 1/2 and multiply it. The final answer is:
p = 2r/m²