The demand function for a certain item is $$x = p^{2}e^{-(p+7)}$$ Use interval notation to indicate the range of prices corresponding to elastic, inelastic, and unitary

NOTE: When using interval notation in WeBWorK, remember that:
        You use 'I' for $\infty$ and '-I' for $-\infty$.
        And use 'U' for the union symbol.
a) The range of prices for elastic is

b) The range of prices for inelastic is

a) The prices for unitary is