F.5 maths equations

Question1:
A factory which produces paints installs a machine. The amount P (in litre) of paint produced per month by the machine after x months can be given by the formula
P = 11000(2^-0.02x) - 8000(2^-0.04x) - 3000

At most for how many months can the machine produce paint?

Question 2:
A player throws a tennis ball upward at a speed of 20 m/s and at an angle @ to the horizontal. When the ball is 12 m from the player horizontally, the height H m reached by the ball can be found by the formula
H = 12tan@ - (9/5)(1 + tan^2 @)

Given that the ball can reach a height of 5 m, what is the maximum value of @?