An ideal discrete-time lowpass filter with cutoff frequency c = 2/5 was designed using impulse invariance

An ideal discrete-time lowpass filter with cutoff frequency ω_c = 2π/5 was designed using impulse invariance from an ideal continuous-time lowpass filter with cutoff frequency Ω_c = 2π (4000) rad/s. What was the value of T? Is this value unique? If not, find another value of T consistent with the information given.