5) Knowing that, for any complex value q. Σ=1+9+9+ -0 = iff q<1. and considering u[n] being the unit step function (u[n]=1 for n>=0 and u[n]=0 for n<0), answer the questions below a) what is the DTFT of x[n] = b² u[n], where 0<b<1 ? b) what is the DTFT of x[n] = bu[n-1], where 0<b<1 ? TIP: write the formula for the DTFT for x[n] and try to add a term to the summation so that you get the geometric sum above. c) What is the DTFT of y[n] = bu[n-1] b u[n-4], where 0<b<1? TIP: recall the linearity property and, to compute the DTFT of each term, use your answer to 5)- a), replace be with bb, and use the time-shifting property.