Calculate the present value of the following future cash inflows discounted at 10 percent: (a) $1,000 a year for years 1 through 10; (b) $1,000 a year for years 5 through 10; and (c) $1,000 a year for years 1 through 3, nothing in years 4 through 5, then $2,000 a year for years 6 through 10.