Real World Calc Problem (Related Rates/Differential)

The diagram has theta on the bottom right angle between the base and hypotenuse.
From what I have so far:
1) Andrew's distance after 10 seconds: 30ft*10sec = 300ft. Brian's distance: a(t) = 5t^2, v(t) = 25t, v(10) = 250ft. Using pythagorean theorem I get sqrt[550] ?
2) I'm finding d(theta)/dt when height of triangle is 30ft. tan(theta) = 30/v. v= 30/tan(theta). dv/dt = -30csc2(theta)*d(theta/dt). From what I understand, dv/dt is andrew's rate of change so it is 30ft/sec. 30/-30csc2(theta) = d(theta)/dt. -30csc2(theta) should be -30*(hypotenuse/30). But then I don't know Andrew's distance to calculate the hypotenuse so is there a way to find out from Brian's 30ft travel?
3) The triangle has a constant base 25 and the height is increasing at 5ft/sec. A=1/2(b)(h) for triangle area. A(t)= 1/2*h(t)*b since area is changing due to the rate that height is changing. Taking derivative of both sides dA/dt = 1/2*b*db/dt. Solving for dA/dt, it is (1/2)*(25)*5. So the change in area's shape is 25/2?
4) No idea how to start here honestly.

/r/MathHelp Thread