Please help solve all parts! Thanks!

Find the present value (as of today) of each of the following perpetuities. The interest rate is 4% per year. I a) A perpetuity that Yvill pay $80 per year forever, starting one year from now Tf b) A perpetuity that will pay $80 per year forever, starting today c) A perpetuity that will pay $80 per year forever, starting two years from now d d) A perpetuity that will pay $80 per year forever, starting five years from now I