Given the following two functions. qa=50+p. qb=200-4p. (a) identify which is the supply function of demand function(b) what is the is equilibrium price of the quantity(c) what is the price elasticity of supply for this

(A) The supply function generally is considered to have positive slope. Qa has positive slope. Qb has negative slope, so is probably the demand function.
  supply function: Qa
  demand function: Qb

(B) The equilibrium price is the price that makes supply equal to demand.
  Qa = Qb
  50 +p = 200 -4p
  5p = 150
  p = 30
The equilibrium price is 30.

(C) The price elasticity of supply is computed as
  Es = (dQa/dp)·(P/Qa) = 1·p/(50+p)
  Es = p/(50+p)

At p=30, the numerical value is Es = 30/80 = 3/8. Qualitatively, the supply is inelastic.

What are the statements?