Choose the correct option for the following Assertion (A) and Reason (R).

For n moles of an ideal gas, the change in internal energy can be written as ΔU = nCᵥ[$T_{f}$-$T_{i}$] = [nR /(γ-1)][$T_{f}$-$T_{i}$], where γ = Cₚ/Cᵥ.

The relation between the number of degrees of freedom f and γ is γ = 1+2/f.