One mole of an ideal gas whose adiabatic exponent equals undergoes a process in which the gas

One mole of an ideal gas whose adiabatic exponent equals γ undergoes a process in which the gas pressure relates to the temperature as p = aTa, where a and a are constants. Find:
(a) The work performed by the gas if its temperature gets an increment ΔT;
(b) The molar heat capacity of the gas in this process; at what value of a will the heat capacity be negative?